Optical element and method for manufacturing the same

ABSTRACT

A method for manufacturing an optical element includes the steps of: providing a first material including a precursor of a first energy curable resin which contains fine particles of a transparent conductive material on a transparent substrate, curing the first material by light irradiation, and performing a heat treatment on the cured first material. In the method described above, the cured first material processed by the heat treatment is again processed by light irradiation.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Divisional of U.S. patent application Ser. No.15/802,205 filed Nov. 2, 2017, which is a Continuation of U.S. patentapplication Ser. No. 13/607,438 filed Sep. 7, 2012, which claimspriority to Japanese Patent Application No. 2011-211112 filed Sep. 27,2011, each of which are hereby incorporated by reference in theirentireties.

BACKGROUND OF THE INVENTION Field of the Invention

The present invention relates to an optical element used for a camera, avideo, and the like and a method for manufacturing an optical element.

DESCRIPTION OF THE RELATED ART

Heretofore, in a refractive optical system using the refraction oflight, lenses formed from glass materials having different dispersioncharacteristics are used together in combination to reduce the chromaticaberration. For example, in the case of an object lens of a telescope orthe like, a glass material having low dispersion and a glass materialhaving high dispersion are used in combination as a positive lens and anegative lens, respectively, to correct the chromatic aberration whichappears on the axis. However, in the case in which the configuration oflenses and the number thereof are limited and/or the case in which glassmaterials to be used are limited, it has been difficult to sufficientlycorrect the chromatic aberration in some cases.

A. D. Kathman and S. K. Pitalo have disclosed a technique in “BinaryOptics in Lens Design”, International Lens Design Conference 1990, SPIEVol. 1354, pp. 297 to 309 (hereinafter referred to as “Non-PatentDocument 1”) in which a refractive optical element having a refractivesurface and a diffractive optical element having a diffraction gratingare used in combination to suppress the chromatic aberration with asmaller number of lenses. The technique thus disclosed utilizes aphysical phenomenon that the chromatic aberration to light having acertain reference wavelength occurs in the opposite direction between arefractive surface and a diffractive surface of optical elements. Inaddition, by changing the period of the diffraction grating, which iscontinuously formed in a diffractive optical element, the samecharacteristic as that of an aspherical lens can be obtained.

However, one light ray incident on a diffractive optical element isdivided into plural light rays of different orders by a diffractionfunction. At this stage, diffracted light rays of orders other than adesigned order are focused on locations different from that of the lightray of the designed order, thereby causing the generation of flare.

According to Japanese Patent Laid-Open No. 2008-203821 (hereinafterreferred to as “Patent Document 1”), by using an optical material havingrelatively low refractive index and high dispersion and an opticalmaterial having relatively high refractive index and low dispersion, alight flux in a use wavelength region is concentrated in a specificorder (hereinafter referred to as “designed order”), and the intensitiesof diffracted light rays of diffraction orders other than the designedorder are suppressed, so that the generation of flare is prevented.

In Patent Document 1, as the optical material having relatively lowrefractive index and high dispersion, a material having a low refractiveindex n_(d) (1.48<n_(d)<1.57), high refractive index dispersionrepresented by Abbe's number ν_(d) (14<ν_(d)<28), and a low second orderdispersion characteristic θ_(gF) (0.34<θ_(gF)<0.47) is used. Inaddition, as the optical material having relatively high refractiveindex and low dispersion, a material having a high refractive index(1.54<n_(d)<1.63) and low refractive index dispersion (44<ν_(d)<57) isused. According to Patent Document 1, when the optical material havingrelatively low refractive index and high dispersion and the opticalmaterial having relatively high refractive index and low dispersion areformed into shapes by ultraviolet curing or the like, diffractionefficiency can be improved in a wide wavelength range over the wholevisible region.

The optical material having low refractive index and high dispersion ofPatent Document 1 can be obtained in such a way that after a transparentconductive metal oxide in the form of fine particles which has highrefractive index dispersion and a low second order dispersioncharacteristic is mixed with and dispersed in a binder resin having alow refractive index to form a composite material, this compositematerial is cured by ultraviolet light. In addition, as the transparentconductive metal oxide, transparent conductive metal oxides, such asindium tin oxide (ITO), have been disclosed.

An optical element, such as a multilayer diffractive optical element,which partially uses a dispersion material containing fine particles ofa transparent conductive material, such as ITO, shows a high diffractionefficiency state over the whole visible region. However, in useenvironment, the optical property, that is, the refractive index, of thedispersion material containing fine particles of a transparentconductive material is changed. By the change in the refractive index,the optical properties of the optical element are degraded. For example,in the case of a multilayer diffractive optical element, highdiffraction efficiency over the whole visible region is decreased.

SUMMARY OF THE INVENTION

In consideration of the background art as described above, aspects ofthe present invention provide an optical element, such as a multilayerdiffractive optical element, which uses a dispersion material containingfine particles of a transparent conductive material, such as ITO, andwhich suppresses the change in the properties (light resistance, agingresistance, and the like) caused by the environment of the opticalelement. Aspects of the present invention also provide a method formanufacturing an optical element.

Aspects of the present invention provide a method for manufacturing anoptical element comprising: providing on a transparent substrate a firstmaterial including a precursor of a first energy curable resin whichcontains fine particles of a transparent conductive material; curing thefirst material by light irradiation; and performing a heat treatment onthe cured first material. In the method described above, the cured firstmaterial processed by the heat treatment is again processed by lightirradiation (hereinafter referred to as “post light irradiation” in somecases).

Aspects of the present invention also provide a method for manufacturingan optical element comprising: providing on a transparent substrate asecond material including a precursor of a second energy curable resin;curing the second material by light irradiation; providing on the curedsecond material a first material including a precursor of a first energycurable resin which contains fine particles of a transparent conductivematerial; curing the first material by light irradiation; and performinga heat treatment on the cured first and second materials. In the methoddescribed above, the cured first and the second materials processed bythe heat treatment are again processed by light irradiation (post lightirradiation).

Aspects of the present invention also provide an optical elementcomprising: a first member including fine particles of a transparentconductive material on a first transparent substrate; and a secondtransparent substrate provided on the first member, and in this opticalelement, the first member is provided with a layer at a portion incontact with the air which inhibits permeation of oxygen and which hasan oxygen permeability of 2.0×10⁻¹¹ P/cm³·cm·(cm²·s·cmHg)⁻¹ or lessmeasured by a high-vacuum pressure difference method.

Aspects of the present invention also provide an optical element, suchas a multilayer diffractive optical element, which uses a dispersionmaterial containing fine particles of a transparent conductive material,such as ITO, and which suppresses the change in the properties (lightresistance, aging resistance, and the like) caused by the environment ofthe optical element and a method for manufacturing an optical element.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B are each a schematic view of an embodiment of an opticalelement according to aspects of the present invention.

FIGS. 2A and 2B are each a schematic view showing a method for formingan optical element for refractive index measurement according to aspectsof the present invention.

FIGS. 3A and 3B are each a schematic view of a post light irradiationstep of the optical element for refractive index measurement accordingto aspects of the present invention.

FIG. 4A is a graph showing a spectrum of a high-pressure mercury lampfor an optical element of an example according to aspects of the presentinvention obtained through a quartz glass.

FIG. 4B is a graph showing a spectrum of a high-pressure mercury lampfor an optical element of an example according to aspects of the presentinvention obtained through an S-TIH11 glass substrate.

FIGS. 5A to 5E are each a schematic view of a method for forming anoptical element for refractive index measurement according to aspects ofthe present invention.

FIGS. 6A and 6B are each a schematic view of a method for forming amultilayer diffractive optical element according to aspects of thepresent invention.

FIGS. 7A to 7E are each a schematic view of the method for forming amultilayer diffractive optical element according to aspects of thepresent invention.

FIG. 8 is a graph showing spectra obtained in a light resistance testwith and without through a 390 nm-cut filter.

FIGS. 9A to 9E are each a schematic view of a method for forming amultilayer diffractive optical element according to Example 10.

FIG. 10 is a schematic view of one example of an optical element of asecond embodiment according to aspects of the present invention.

FIGS. 11A and 11B are each a schematic view of one example of theoptical element of the second embodiment according to aspects of thepresent invention.

DESCRIPTION OF THE EMBODIMENTS

Hereinafter, embodiments according to aspects of the present inventionwill be described in detail.

First Embodiment

In a method for manufacturing an optical element according to a firstembodiment, after a first material including a precursor of a firstenergy curable resin which contains fine particles of a transparentconductive material is provided on a transparent substrate and is thencured by light irradiation, a heat treatment is performed, andfurthermore, the cured first material processed by the heat treatment isagain processed by light irradiation (hereinafter referred to as “postlight irradiation” in some cases). An optical element obtained by themanufacturing method according to aspects of the present invention whichuses a material containing a transparent conductive material dispersedtherein can suppress the change in the refractive index/transmission ata long wavelength caused by light, such as ultraviolet light.

In addition, the method for manufacturing an optical element accordingto the first embodiment includes the following two methods formanufacturing a multilayer diffractive optical element.

(1) In a method for manufacturing an optical element comprising:providing on a transparent substrate a first material including aprecursor of a first energy curable resin which contains fine particlesof a transparent conductive material; curing the first material by lightirradiation; providing a second material including a precursor of asecond energy curable resin on the cured first material; curing thesecond material by light irradiation, and performing a heat treatment onthe cured first and second materials, the method for manufacturing anoptical element further comprises again performing light irradiation(post light irradiation) on the cured first and the second materialswhich are processed by the heat treatment.

(2) In a method for manufacturing an optical element comprising:providing on a transparent substrate a second material including aprecursor of a second energy curable resin; curing the second materialby light irradiation; providing a first material including a precursorof a first energy curable resin which contains fine particles of atransparent conductive material on the cured second material; curing thefirst material by light irradiation; and performing a heat treatment onthe cured first and second materials, the method for manufacturing anoptical element further comprises again performing light irradiation(post light irradiation) on the cured first and the second materialswhich are processed by the heat treatment.

In the multilayer diffractive optical element obtained by themanufacturing method of this embodiment, a multilayer using the materialin which the fine particles of the transparent conductive material aredispersed can suppress the change in the refractive index/transmissionat a long wavelength caused by light, such as ultraviolet light. In themultilayer diffractive optical element described above, the opticalproperties of the cured first material are preferably relatively lowrefractive index and high dispersion, and the optical properties of thecured second material are preferably relatively high refractive indexand low dispersion.

The present inventors discovered that by a photochemical reaction of aresin caused by ultraviolet light and visible light having a shortwavelength, each of which is incident on an optical element in generaluse environment, a dispersion material containing fine particles of atransparent conductive material, such as ITO, generates radicals. Thegenerated radicals are trapped by the fine particles of the transparentconductive material to function as carriers thereof. Hence, the opticalproperties are influenced thereby. In particular, the present inventorsdiscovered that the refractive index and the absorption in the visibleregion at a long wavelength side (λ=500 to 700 nm) are significantlychanged. As a result, the present inventors found a problem in that bythe change in the refractive index of the dispersion material containingfine particles of a transparent conductive material, a high diffractionefficiency state of the optical element at an initial stage is shiftedfrom the diffraction conditions.

The present inventors discovered that when an optical element which usesa dispersion material containing fine particles of a transparentconductive material, such as ITO, is formed, some of radicals generatedin energy curing by ultraviolet light or the like are trapped by the ITOfine particles to contribute to the optical properties as carriers. Inaddition, besides the increase in number of carriers by the increase innumber of trapped radicals, it was also found that the number ofcarriers is increased by excitation. It was found that the carriersgenerated by excitation inhibit the carriers generated by the trappedradicals from reaching a saturated level. In addition, it was also foundthat after the carriers generated by excitation are made to disappear byperforming a heat treatment (annealing) or the like, when lightirradiation is again further performed in such a way that energyirradiation is performed by ultraviolet light or the like, the radicalstrapped by the fine particles of the transparent conductive materialreach an approximately saturated level. When such energy irradiation isperformed, even if an optical element is placed in environment ofultraviolet light or the like, the change in the optical propertiesthereof can be suppressed.

In the method for manufacturing an optical element using a dispersionmaterial containing fine particles of a transparent conductive materialof this embodiment, after the dispersion material is formed into a finalshape of the optical element by energy curing of light irradiation, aheat treatment is performed, and light irradiation is again performed(post light irradiation). Accordingly, this embodiment is able topropose a method for manufacturing an optical element which can suppressthe change in the optical properties of the optical element even inenvironment of ultraviolet light or the like.

<Transparent Conductive Material>

In the first material according to aspects of the present invention, thefine particles of the transparent conductive material (hereinaftersimply referred to as “fine particles” in some cases) are contained. Inthe second material, fine particles of a transparent conductive materialmay or may not be contained.

As preferable examples of the fine particles of the transparentconductive material contained in the precursor of the energy curableresin according to aspects of the present invention, for example, theremay be mentioned zinc oxide (ZnO), indium oxide, tin oxide, antimonyoxide, indium tin oxide (ITO), antimony-doped tin oxide (ATO),zinc-doped indium oxide (IZO), aluminum-doped zinc oxide (AZO), andfluorine-doped tin oxide (FTO). Among those mentioned above, indium tinoxide (ITO), antimony-doped tin oxide (ATO), and zinc oxide arepreferably used. Among the currently existing materials, indium tinoxide (ITO) has a low second-order dispersion characteristic (θ_(gF))and in particular, has the highest transparency. However, when amaterial having a low second-order dispersion characteristic (θ_(gF))and more excellent transparency than that of indium tin oxide (ITO) isdiscovered in future, the use of this material is not limited.

In addition, in accordance with a solvent in which a monomer formed intoa base resin of the precursor and the fine particles are dispersed inadvance, various surface treatment agents and/or dispersants arepreferably used on the surfaces of the fine particles.

As the average particle diameter of the fine particles of thetransparent conductive material, a particle diameter that has no adverseinfluence on the optical transmittance, the optical scattering, and thelike is preferable. The average particle diameter is 1 to 100 nm,preferably 2 to 30 nm, and more preferably 2 to 20 nm. However, forexample, even if the average particle diameter is 20 nm or less, whenthe distribution of the particle diameter is broad, and the volumefraction of particles having a particle diameter of more than 30 nm is5% or more of all the fine particles (including the case in which fineparticles are aggregated), the optical scattering is considerablyadversely affected thereby. In the case described above, by a filteringtreatment using a filter having a pore size relatively smaller than thesize of particles to be removed, unnecessary large fine particles arepreferably removed. As the state in which the fine particles areremoved, a state (fine particle dispersion liquid) in which fineparticles are dispersed in a solvent before a monomer formed into a baseresin is mixed, a state in which the base resin is dissolved in the fineparticle dispersion liquid, or although dependent on the viscosity, astate in which the solvent is removed from the state described above toform a non-solvent mixture of the base resin and the fine particles ispreferable.

The content of the fine particles of the transparent conductive materialcontained in the cured first material is 1 to 29 percent by volume withrespect to the total of the first material and is preferably 5 to 20percent by volume. When the content is less than 1 percent by volume, itis not preferable since the optical properties cannot be effectivelyobtained. In addition, when the content is more than 29 percent byvolume, it is also not preferable since the moldability is degraded.

If needed, a surface treatment is preferably performed on the fineparticles of the transparent conductive material. The surface treatmentmay be performed when the fine particle are synthesized or formed or maybe performed separately after the fine particles are obtained.

In addition, in order to prevent the fine particles of the transparentconductive material from being aggregated, a surface treatment agentand/or a dispersant (surfactant) is preferably used to form a uniformdispersion state. In general, it has been known that when fine particlesare dispersed in a solvent or a resin using a surface treatment agentand/or a dispersant, different dispersion states are obtained dependingon the type, amount, molecular weight, polarity, affinity, and the likeof the surface treatment agent and/or the dispersant to be added. As thesurface treatment agent and/or the dispersant that can be used inaspects of the present invention, a pigment derivative, a resin typeagent, and an activator type agent may be preferably used. In thisembodiment, as the surface treatment agent and/or the dispersant, acationic, a weak cationic, a nonionic, or an ampholytic surfactant iseffectively used. In particular, a polyester-based, anε-caprolactone-based, a polycarboxylic acid salt, a polyphosphate salt,a hydrostearate salt, an amidosulfonate salt, a polyacrylate salt, anolefin-maleate salt copolymer, an acrylic-maleate salt copolymer, analkylamine acetate salt, an alkyl fatty acid salt, a fatty acidpoly(ethylene glycol) ester-based, a silicone-based, and afluorine-based surfactant may be used; however, according to aspects ofthe present invention, at least one type of basic compounds selectedfrom ammonium and organic amines is preferably used. In particular, forexample, there may be mentioned DISPERBYK-161, 162, 163, and 164 ofDISPERBYK Series (manufactured by BYK Japan KK), Solsverse 3000, 9000,17000, 20000, 24000, and 41090 of Solsverse Series (manufactured byZenega Co., Ltd.), and PO or EO modified products of alkylamines, suchas TAMN-15, of TAMN Series (manufactured by Nikko Chemicals Co., Ltd.).The addition amount of the surface treatment agent and/or the dispersantis changed depending roughly on the type of surface treatment agentand/or dispersant, the type of fine particles, the surface area thereof(diameter of fine particles), the type of dispersion resin in which thefine particles are mixed, and the type of dispersion solvent. As theaddition amount of the surface treatment agent and/or the dispersant,with respect to the weight of the fine particles, the amount ispreferably in a range of 0.1 to 35.0 percent by weight. When theaddition amount of the dispersant is excessive, since cloudiness occursthereby, the optical scattering is generated, and in addition, theproperties (refractive index, Abbe's number, second-order dispersioncharacteristic, elastic modulus, and the like) of the composition whichcontains the fine particle are unnecessarily degraded. The additionamount is preferably in a range of 4.0 to 25.0 percent by weight. Inaddition, the surface treatment agents and/or the dispersants may beused alone, or at least two types thereof may be used in combination.

<Dispersion Solvent>

As a dispersion solvent that can be used in aspects of the presentinvention, in order to dissolve a monomer, an oligomer, and the like,each of which is a resin composition component of the precursor of theenergy curable resin, or to disperse the fine particles of thetransparent conductive material in a solvent, if needed, the solvent isused to dissolve a surface treatment agent and/or a dispersant.

As the dispersion solvent, for example, there may be mentioned aromatichydrocarbons, such as toluene, benzene, and xylene; alcohols, such asethanol and isopropyl alcohol; alicyclic hydrocarbons such ascyclohexane; acetates, such as ethyl acetate and butyl acetate; ketones,such as acetone and methyl ethyl ketone; amides, such as dimethylformamide (DMF), dimethyl acetamide (DMAc), and N-methylpyrrolidone(NMP); aliphatic hydrocarbons, such as hexane and octane; ethers, suchas diethyl ether and butyl carbitol; and halogenated hydrocarbons, suchas dichloromethane and tetrachloro carbon; however, the dispersionsolvent is not limited to those mentioned above. In accordance with theaffinity of the fine particles to be used and the affinity of thesurface treatment agent and/or the dispersant to be used, the dispersionsolvent may be appropriately selected. In addition, the dispersionsolvents may be used alone, or at least two types thereof may be used incombination as long as the dispersibility is not adversely influenced.

<Precursor of Energy Curable Resin>

Next, the precursor of the energy curable resin according to aspects ofthe present invention will be described. The precursor of the firstenergy curable resin is used for the first material, and the precursorof the second energy curable resin is used for the second material.Although a resin composition (monomer and oligomer) of the precursor ofthe first energy curable resin may be the same as or different from aresin composition (monomer and oligomer) of the precursor of the secondenergy curable resin, when it is attempted to suppress the change in theproperties of the first material with time by oxygen diffusion in theoptical element, in order to control the oxygen permeability and theoxygen solubility of the second material, the compositions of the firstand the second materials and the ratio therebetween must be adjusted.

According to aspects of the present invention, as the precursor of theenergy curable resin, a monomer or an oligomer, which is a bindercomponent as the base resin, is used. As the monomer or the oligomer, amaterial is preferable which is compatible with a surface treatmentagent, a dispersant, and a solvent in which for example, the fineparticles of the transparent conductive material are dispersed.

The monomer described above is not particularly limited, as long asbeing a compound having at least one unsaturated group, such as a doublebond or a triple bond, in its molecule. As particular examples of amonomer or an oligomer of the compound having an unsaturated group, forexample, there may be mentioned monofunctional acrylates ormethacrylates, such as 1,4-divinylcyclohexane, 1,4-cyclohexanedimethanol divinyl ether, 4,4-dimethyl-kept-1-en-6-yne, divinylbenzene,1,6-divinylnaphthalene, N-vinylpyrrolidone, N-vinylcaprolactam,ethoxylated bisphenol A divinyl ether, propoxylated bisphenol A divinylether, polyethylene glycol) mono(meth)acrylate, polypropylene glycolmono(meth)acrylate, and phenoxyethyl (meta)acrylate. In addition, thefollowing polyfunctional acrylates or methacrylates may also bementioned as particular examples. That is, for example, there may bementioned poly(ethylene glycol) di(meth)acrylate, poly(propylene glycol)di(meth)acrylate, trimethylolethane tri(meth)acrylate, neopentyl glycoldi(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritoltetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, hexanedioldi(meth)acrylate, and tri(acryloxyethyl)isocyanurate; compounds whichare (meth)acrylated after ethylene oxide or propylene oxide is added toa polyalcohol, such as glycerin or trimethylolethane; urethane acrylatesas disclosed in Japanese Patent Publication Nos. 48-4178 and 50-6034;polyester acrylates disclosed in Japanese Patent Laid-Open No. 48-64183and Japanese Patent Publication Nos. 49-43191 and 52-30490; and epoxyacrylates obtained by a reaction between an epoxy resin and(meth)acrylic acid.

In the case of fluorinated monomers, as monomers forming preferableresins, a fluorinated acrylic monomer, a fluorinated methacrylicmonomer, a fluorinated epoxy monomer, and a fluorinated vinyl monomermay be mentioned. In particular, as the monomers and analogs thereof,there may be mentioned 2,2,2-trifluoroethyl acrylate,2,2,3,3,3-pentafluoropropyl acrylate, 2-(perfluorobutyl)ethyl acrylate,3-perfluorobutyl-2-hydroxypropyl acrylate, 2-(perfluorohexyl) ethylacrylate, 3-perfluorohexyl-2-hydroxypropyl acrylate,2-(perfluorooctyl)ethyl acrylate, 3-perfluorooctyl-2-hydroxypropylacrylate, 2-(perfluorodecyl) ethyl acrylate,2-(perfluoro-3-methylbutyl)ethyl acrylate,3-(perfluoro-3-methylbutyl)-2-hydroxypropyl acrylate,2-(perfluoro-5-methylhexyl)ethyl acrylate,3-(perfluoro-5-methylhexyl)-2-hydroxypropyl acrylate,2-(perfluoro-7-methyloctyl)ethyl acrylate,3-(perfluoro-7-methyloctyl)-2-hydroxypropyl acrylate,1H,1H,3H-tetrafluoropropyl acrylate, 1H,1H,5H-octafluoropentyl acrylate,1H,1H,7H-dodecafluoroheptyl acrylate, 1H,1H,9H-hexadecafluorononylacrylate, 1H-1-(trifluoromethyl) trifluoroethyl acrylate,1H,1H,3H-hexafluorobutyl acrylate,2,2,3,3,4,4,5,5-octafluorohexane-1,6-diacrylate, 2,2,2-trifluoroethylmethacrylate, 2,2,3,3,3-pentafluoropropyl methacrylate,2-(perfluorobutyl) ethyl methacrylate, 3-perfluorobutyl-2-hydroxypropylmethacrylate, 2-(perfluorohexyl)ethyl methacrylate,3-perfluorohexyl-2-hydroxypropyl methacrylate, 2-(perfluorooctyl)ethylmethacrylate, 3-perfluorooctyl-2-hydroxypropyl methacrylate,2-(perfluorodecyl)ethyl methacrylate, 2-(perfluoro-3-methylbutyl)ethylmethacrylate, 3-(perfluoro-3-methylbutyl)-2-hydroxypropyl methacrylate,2-(perfluoro-5-methylhexyl) ethyl methacrylate,3-(perfluoro-5-methylhexyl)-2-hydroxypropyl methacrylate,2-(perfluoro-7-methyloctyl)ethyl methacrylate,3-(perfluoro-7-methyloctyl)-2-hydroxypropyl methacrylate,1H,1H,3H-tetrafluoropropyl methacrylate, 1H,1H,5H-octafluoropentylmethacrylate, 1H,1H,7H-dodecafluoroheptyl methacrylate,1H,1H,9H-hexadecafluorononyl methacrylate,1H-1-(trifluoromethyl)trifluoroethyl methacrylate,1H,1H,3H-hexafluorobutyl methacrylate,2,2,3,3,4,4,5,5-octafluorohexane-1,6-dimethacrylate,hexafluoroepoxypropane, 3-perfluorobutyl-1,2-epoxypropane,3-perfluorohexyl-1,2-epoxypropane, 3-perfluorooctyl-1,2-epoxypropane,3-perfluorodecyl-1,2-epoxypropane,3-(perfluoro-3-methylbutyl)-1,2-epoxypropane,3-(perfluoro-5-methylhexyl)-1,2-epoxypropane,3-(perfluoro-7-methyloctyl)-1,2-epoxypropane,3-(2,2,3,3-tetrafluoropropoxy)-1,2-epoxypropane,3-(1H,1H,5H-octafluoropentyloxy)-1,2-epoxypropane,3-(1H,1H,7H-dodecafluoroheptyloxy)-1,2-epoxypropane,3-(1H,1H,9H-hexadecafluorononyloxy)-1,2-epoxypropane, and1,4-bis(2′,3′-epoxypropyl)-perfluoro-n-butane.

These monomers may be used alone, or at least two types thereof may beused in combination. As a resin composition, a fluorinated polymer resinmay also be selected. In addition, as a copolymer, among materialsmanufactured by Central Glass Co., Ltd., Nos. 702C, 703C, 704C, 705C,706C, 707C, and analogs thereof may be mentioned.

Fluorinated monomers having a polymerizable functional group in itsmolecule, each of which functions as the monomer of the resincomposition of the first material, may be used alone, or at least twotypes thereof may be used in combination. Alternatively, at least one ofthe fluorinated monomers may be used together with the acrylate and/orthe methacrylate mentioned above.

The energy curable resin forming the first material is preferably atleast one radical curable resin selected from the group consisting of anacrylic resin, a vinyl resin, and an epoxy resin.

The content of the resin composition (monomer and oligomer) of theprecursor of the energy curable resin contained in the first material is30 to 98 percent by volume with respect to the total first material andis preferably 50 to 90 percent by volume. When the content is less than30 percent by volume, it is not preferable since the moldability isdegraded. In addition, when the content is more than 98 percent byvolume, since the ratio of the conductive fine particles is relativelydecreased, it is not preferable since the optical properties are notsufficiently obtained.

As a method for performing energy curing of the precursor of the energycurable resin, polymerization can be performed by stimulating aninitiator by a plasma treatment, a heat treatment, or energy of lightsuch as radiation or ultraviolet light. When replica formation of a lensor the like is taken into consideration, photocuring is preferable. Inparticular, as usable photopolymerization initiators, for example,2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone,1-hydroxy-cyclohexyl phenyl ketone,bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide, 4-phenylbenzophenon,4-phenoxybenzophenone, 4,4′-diphenylbenzophenone, and4,4′-diphenoxybenzophenone may be preferably mentioned. When thetransparency of a cured resin is taken into consideration,1-hydroxy-cyclohexyl phenyl ketone is preferably used.

Although the addition amount of the photopolymerization initiator ischanged depending on the addition amount of the fine particles whichabsorb visible light, with respect to the total resin composition of thematerial, the amount is preferably set in a range of 0.01 to 10.00percent by weight. In accordance with the reactivity with a monomer andan oligomer and the wavelength of light irradiation, thephotopolymerization initiators may be used alone, or at least two typesthereof may be used in combination.

Next, steps of preparing the first material and the second materialaccording to aspects of the present invention will be described.

After the surface treatment agent or the dispersant in an appropriateamount is first dissolved in a selected solvent, and the fine particlesare added thereto, a shearing force is applied to the mixture thusprepared to pulverize aggregates of the fine particles, and remainingaggregates are removed by centrifugal separation and a filter treatment,so that a uniform fine particle dispersion liquid is obtained.Subsequently, a photopolymerizable monomer and oligomer and aphotopolymerization initiator are dissolved in the above dispersionliquid. When the monomer and the oligomer are dissolved in the fineparticle dispersion liquid, the solvent, the surface treatment agent,and the dispersant are preferably used in combination so that thedispersion state of the fine particles is not degraded by the additionof the monomer and the oligomer. In addition, if needed, by performing afiltering treatment, aggregated fine particles can be removed.

After it is confirmed that the fine particles are preferably dispersedwithout generating any precipitations thereof, the solvent is removedusing an evaporator. In this step, in accordance with the boiling pointof the solvent, the amount of a remaining solvent, and the like, it ispreferable that the vacuum degree be appropriately adjusted. By rapidevaporation and removal of the solvent, the degree of aggregation of thefine particles may be degraded, and as a result, the dispersibility isdegraded in some cases. In addition, when the solvent is removed at areduced pressure, if needed, heating may be performed so as not todegrade the dispersibility. As described above, the first material orthe second material, which is the precursor used in aspects of thepresent invention, is obtained.

In the first material or the second material thus obtained, a remainingsolvent which cannot be removed may be contained in some cases. Whenthis content is more than 0.1 percent by weight, by a function topromote fine particle migration in energy curing, the gradient index(GI) and the light scattering are increased. Hence, the content of theremaining solvent is preferably 0.1 percent by weight or less. However,when the vacuum degree is excessively high, when heating is performedunder a reduced pressure condition, or when a reduced-pressure step isperformed for a long time, monomers, such as the surface treatmentagent, the dispersant, and the binder component, which are addedtogether with the solvent may also be distilled away in some cases.Hence, in consideration of the molecular weight, the boiling point, thesublimability, and the like of each monomer, the vacuum degree, thetemperature, the process time, and the like must be adjusted.

<Curing by Light Irradiation, Heat Treatment, and Post LightIrradiation>

First, a method for curing the first material and the second material,which are the precursors of the resins, by light irradiation will bedescribed.

When the optical element according to aspects of the present inventionis molded, and as a particular example, when a diffractive opticalelement is molded, a process of forming a mold forming layer using thefirst material of the precursor by a photopolymerization method will bedescribed. When a thin layer structure is formed on a light transmissivematerial to be used for the transparent substrate, for example, a flatglass plate is used as the substrate, and a metal material is used for amold having a shape corresponding to a fine diffraction gratingstructure. After the first material formed of the precursor havingfluidity is pored between the mold and the flat glass plate, the moldand the glass plate are lightly pressed to each other, so that moldformation is performed. While the state described above is maintained,photopolymerization of the first material is performed.

Light irradiation for such a photopolymerization reaction is performedusing light, such as in general ultraviolet light or visible light,having a preferable wavelength in accordance with the mechanism based onradical generation using a photopolymerization initiator. For example,light irradiation is uniformly performed on the molded first material ofthe precursor through the light transmissive material, that is, the flatglass plate, used for the substrate. The amount of light to beirradiated is appropriately selected in accordance with the mechanismbased on the radical generation using a photopolymerization initiatorand the content thereof. Subsequently, the second material of theprecursor is laminated. When it is intended to form a highly efficientdiffractive optical element in the whole visible region, the secondmaterial to be laminated is determined by the optical constants of thefirst layer formed of the first material so as to have high refractiveindex and low dispersion values after the curing as compared to those ofthe first layer. As the second material, a monomer of the resin or amixture containing a monomer and fine particles of zirconia, alumina, orthe like may be used.

However, when a property of inhibiting oxygen diffusion and/or afunction to absorb oxygen is imparted to the second material, thecomposition of the monomer thereof, and the surface treatment agentand/or the dispersant for the fine particles of zirconia and alumina arelimited. In particular, a general dispersant having a high molecularweight cannot be used, and for example, a surface treatment agent havinga low molecular weight and forming a strong covalent bond with themonomer is preferable. The reason for this is that the glass transitiontemperature of the second material is increased to inhibit the diffusionof oxygen. After the second material of the precursor is arranged on thetransparent substrate, and the polymer molded body (diffraction gratingor the like) of the first material is lightly pressed on the secondmaterial, while the state as described above is maintained,photopolymerization of the second material is performed. Lightirradiation for such a photopolymerization reaction is performed usinglight, such as in general ultraviolet light or visible light, having apreferable wavelength in accordance with the mechanism based on theradical generation using a photopolymerization initiator. For example,light irradiation is uniformly performed on the molded second materialof the precursor from a side of a light transmissive material used asthe transparent substrate, that is, from a transparent substrate side ofthe first material or a transparent substrate side of the secondmaterial. The amount of light to be irradiated is appropriately selectedin accordance with the mechanism based on the radical generation using aphotopolymerization initiator and the content thereof. When the secondmaterial is cured by the above method, an optical element shown in FIG.1A or 1B is obtained.

In the above description, although the optical element is formed bycuring the second material of the precursor on the cured first material,conversely, the optical element shown in FIG. 1A or 1B may be formed bycuring the first material of the precursor on the cured second material.

In the figure, reference numeral 1 indicates a relatively highrefractive index and low dispersion layer of the cured second material,reference numeral 2 indicates a relatively low refractive index and highdispersion layer of the cured first material, and reference numeral 3indicates a transparent substrate layer. FIG. 1A and FIG. 1B show amultilayer diffractive optical element 100 and an optical element 110,respectively.

Next, a heat treatment performed after the first material and the secondmaterial of the precursors are cured by light irradiation will bedescribed.

In general, since the cured products obtained by curing the first andthe second materials shown in FIGS. 1A and 1B each have a stressgenerated in the curing, the residual stress is reduced by a heattreatment. The heat treatment is performed in particular at 60° C. to120° C. for 24 to 120 hours. The temperature is preferably 70° C. to 90°C.

Next, the post light irradiation performed after the heat treatment willbe described.

After the above heat treatment is performed, since the post lightirradiation is performed, an optical element having a small change inthe optical properties caused by ultraviolet light, short-wavelengthvisible light, and the like can be formed.

The post light irradiation preferably includes light having a wavelengthof 300 to 400 nm, and the amount of irradiation light having awavelength of 300 to 400 nm is preferably 12 to 150 J.

In addition, it is preferable that the post light irradiation includelight having a wavelength of 300 to 400 nm, the ratio of light having awavelength of 300 to 350 nm be 0% to 10% of the whole light, and theamount of irradiation light having a wavelength of 300 to 400 nm be 12to 150 J. Accordingly, an optical element having a small change in theoptical properties caused by ultraviolet light, short-wavelength visiblelight, and the like can be formed.

By using an optical element formed by the manufacturing method accordingto aspects of the present invention, there can be provided a method formanufacturing a diffractive optical element in which layers formed ofmaterials having different refractive indices and wavelength dispersionsare laminated on a substrate so as to increase the diffractionefficiency of a specific order (designed order) in the entire usewavelength region and to prevent the change in the properties caused byvisible light or ultraviolet light and the change with time caused byoxygen diffusion from a peripheral portion.

According to the method for manufacturing an optical element accordingto aspects of the present invention, since layers formed of materialshaving different refractive indices and wavelength dispersions arelaminated on a substrate, the diffraction efficiency of a specific order(designed order) can be increased in the entire use wavelength region,and an optical element can be provided which prevents properties thereoffrom being changed by visible light or ultraviolet light and moistureabsorption. Accordingly, the present invention can be used for anoptical element, a diffractive optical element, a multilayer diffractiveoptical element, and an optical system, in particular, an image formingoptical system, such as a camera and a video camera.

Second Embodiment

An optical element according to a second embodiment is an opticalelement having a first member containing fine particles of a transparentconductive material and a second transparent substrate in this order ona first transparent substrate, and the first member is provided with alayer which inhibits permeation of oxygen at a portion in contact withthe air and which has an oxygen permeability of 2.0×10⁻¹¹P/cm³≠cm·(cm²·s·cmHg)⁻¹ or less measured by a high-vacuum pressuredifference method. With reference to FIG. 10, the optical element of thesecond embodiment will be described. In FIG. 10, a first member 22containing fine particles of a transparent conductive material and asecond transparent member 23 are provided on a first transparent member21. The first member 22 containing fine particles of a transparentconductive material is provided with a layer 24 which inhibitspermeation of oxygen so as not to be in contact with the air.

The optical element of the second embodiment using a material in whichthe transparent conductive material is dispersed can suppress the changewith time in the refractive index/transmittance at a long wavelengthwhich is caused by oxidation of the transparent conductive material.

The present inventors discovered that the refractive index and theabsorption at a long wavelength side (λ=500 to 700 nm) in the visibleregion of an optical material using fine particles of a transparentconductive material, such as ITO, are considerably changed from theperiphery of an element, and these changes progress to the inside withtime. By this change in the refractive index, the optical properties areshifted from the diffraction condition, and the element performance isdegraded. In particular, the present inventors found that the elementperformance of an element manufactured by a manufacturing method whichperforms light irradiation at least twice is more considerably degraded.

It is believed that when an optical element using a dispersion materialcontaining fine particles of a transparent conductive material, such asITO, is formed, some of radicals generated in energy curing byultraviolet light or the like and radicals generated by energy ofultraviolet light or the like after the curing are trapped by the fineparticles of the transparent conductive material, such as ITO, and thetrapped radicals have contribution to the optical properties of thedispersion material containing fine particles of a transparentconductive material. In addition, the present inventors also believethat an optical material in which radicals are trapped by the fineparticles of the transparent conductive material, such as ITO, asdescribed above loses the radicals adhered to ITO by diffusion of oxygenfrom the periphery of the element, and hence the fine particles of ITOare returned to the original state. Accordingly, it is believed that thenumber of carriers in the transparent conductive material is changed,and as a result, the optical properties are influenced.

The present inventors discovered that when a layer which inhibits thediffusion of oxygen is provided at a peripheral portion of an opticalelement in contact with the air, the refractive index and the absorptionof an optical material using fine particles of a transparent conductivematerial, such as ITO, at a long wavelength side (λ=500 to 700 nm) inthe visible region are suppressed from being considerably changed, andthese changes progressing to the inside with time can also besuppressed. In addition, the solubility of oxygen in the second materialis preferably equal to or more than (1.4×10⁻³ S/cm³·(cm³·cmHg)⁻¹) thatof the first material. The thickness of the second material ispreferably 1.5 times the average thickness of the first material. Inaddition, the oxygen permeability of the second material is preferablyset to 2.0×10⁻¹¹ P/cm³·cm·(cm²·s·cmHg)⁻¹ or less measured by ahigh-vacuum pressure difference method.

Among optical elements using a dispersion material containing fineparticles of a transparent conductive material, the second embodimentrelates to an optical element which can suppress the change ofproperties of the element with time in common environment by a layer toinhibit the diffusion of oxygen provided at a peripheral portion.

The optical element of the second embodiment may have a first membercontaining fine particles of a transparent conductive material, a secondmember, and a second transparent substrate in this order on a firsttransparent substrate. In addition, the second member may be formed ofthe same material as that of the layer which inhibits permeation ofoxygen. The optical element will be described with reference to FIGS.11A and 11B. In FIG. 11A, the first member 22 containing fine particlesof a transparent conductive material, a second member 25, and the secondtransparent member 23 are provided in this order on the firsttransparent member 21. The first member 22 containing fine particles ofa transparent conductive material is provided with the layer 24 whichinhibits permeation of oxygen at a portion in contact with the air so asnot to be in contact with the air. As shown in FIG. 11B, the layer whichinhibits permeation of oxygen may be formed of the same material as thatof the second member. In FIG. 11B, although the layer 24 which inhibitspermeation of oxygen and the second member are separately provided, thelayer 24 and the second member may be integrally formed.

The solubility of oxygen in the second member is preferably 1.4×10⁻³S/cm³·(cm³·cmHg)⁻¹ or more. When the solubility of oxygen is less than1.4×10⁻³ S/cm³·(cm³·cmHg)⁻¹, the element performance is degraded. Inaddition, the oxygen permeability of the second material is preferably2.0×10⁻¹¹ P/cm³·cm·(cm²·s·cmHg)⁻¹ or less measured by a high-vacuumpressure difference method.

<Transparent Conductive Material>

As the transparent conductive material, the material described in thefirst embodiment may be used.

The content of the fine particles of the transparent conductive materialin the first member is preferably 1 to 29 percent by volume to the firstmember.

<First Member>

The first member preferably contains at least one of an acrylic resin, avinyl resin, and an epoxy resin.

<Optical Element>

In the optical element of the second member, when the refractive indexof the first member is represented by nd1, the Abbe's number of thefirst member is represented by ν1, the refractive index of the secondmember is represented by nd2, and the Abbe's number of the second memberis represented by ν2, nd1<nd2 and ν1<ν2 are preferably satisfied.

The optical element is preferably a multilayer diffractive opticalelement.

<Method for Manufacturing Optical Element>

A method for manufacturing an optical element of the second embodimentcan be performed in a manner similar to that of the method formanufacturing an optical element of the first embodiment. Incidentally,in the method for manufacturing an optical element of the secondembodiment, the post light irradiation is not always required. However,the post light irradiation is preferably performed.

In addition, in the optical element of the second embodiment, thematerials described in the first embodiment may also be used.

EXAMPLES

Hereinafter, preparation of optical materials according to aspects ofthe present invention will be described in detail.

[Preparation of Low Refractive Index and High Dispersion Material][Preparation of Low Refractive Index and High Dispersion Material 11]

First, 51.63 g of a fine-particle dispersion liquid (average particlediameter: 20 nm, concentration of indium tin oxide: 9.96 percent byweight, concentration of a dispersant: 2.19 percent by weight, type ofdispersant: high molecular weight dispersant, manufactured by CIK NanoTech Corporation) in which indium tin oxide (ITO) was dispersed in axylene solvent was mixed with 3.72 g of a mixture as an ultravioletcurable acrylic resin containing 20 percent by weight oftris(2-acryloxyethyl)isocyanurate, 25 percent by weight ofpentaerythritol triacrylate, 40 percent by weight of dicyclopentenyloxyethyl methacrylate, 13 percent by weight of a urethane modifiedpolyester acrylate, and 2 percent by weight of 1-hydroxycyclohexylphenyl ketone. This mixed solution was received in an evaporator, andthe xylene solvent was removed finally at an oil bath temperature of 45°C. and a set pressure of 2 hPas for 20 hours, so that a low refractiveindex and high dispersion material 11 was prepared.

In addition, the particle diameter of the indium tin oxide (ITO) wasmeasured by a laser type particle size analyzer (ELS, manufactured byOtsuka Electronics Co., Ltd.).

In addition, by a thermal gravity analyzer TGA (manufactured byPerkinElmer), the low refractive index and high dispersion material 11was fired, and the inorganic solid component thereof was quantitativelydetermined, so that a content of 51.2 percent by weight was obtained.

The content of a remaining solvent (xylene) measured by a gaschromatography (5890 series II, manufactured by Hewlett Packard) was0.010 percent by weight.

[Preparation of High Refractive Index and Low Dispersion Material 21]

First, 163.3 g of a fine-particle dispersion liquid (average particlediameter: 10 nm, concentration of zirconium oxide: 10.02 percent byweight, concentration of a surface treatment agent: 2.72 percent byweight, type of surface treatment agent: silane coupling agent includinga low molecular weight polymerizable group, manufactured by SumitomoOsaka Cement Company, Limited) in which zirconium oxide was dispersed ina toluene solvent was mixed with 9.20 g of a mixture as an ultravioletcurable acrylic resin containing 20 percent by weight oftris(2-acryloxyethyl)isocyanurate, 25 percent by weight ofpentaerythritol triacrylate, 40 percent by weight of dicyclopentenyloxyethyl methacrylate, 13 percent by weight of a urethane modifiedpolyester acrylate, and 2 percent by weight of 1-hydroxycyclohexylphenyl ketone. This mixed solution was received in an evaporator, andthe toluene solvent was removed finally at an oil bath temperature of45° C. and a set pressure of 3 hPas for 15 hours, so that a highrefractive index and low dispersion material 21 was prepared.

In addition, the particle diameter of the zirconium oxide was measuredby a laser type particle size analyzer (ELS, manufactured by OtsukaElectronics Co., Ltd.). Although the value submitted by Sumitomo OsakaCement Co., Ltd. was 3 to 5 nm, since the laser type particle sizedistribution was obtained by measuring particle diameters including thatof a surface treatment agent, it was estimated the data obtained therebywas different from the actual value.

In addition, by a TGA (manufactured by PerkinElmer), the high refractiveindex and low dispersion material 21 was fired, and the inorganic solidcomponent thereof was quantitatively determined, so that a content of54.5 percent by weight was obtained.

The content of a remaining solvent (toluene) measured by a gaschromatography (5890 series II, manufactured by Hewlett Packard) was0.005 percent by weight or less.

Example 1 <Formation of Optical Element 200 for Refractive IndexMeasurement>

An optical element 200 for refractive index measurement was formed asdescribed below.

First, as shown in FIG. 2A, a spacer 7 having a thickness of 12.5 μm andan ITO fine-particle dispersion material 5 (low refractive index andhigh dispersion material 11) were arranged on a high refractive indexglass (S-TIH11: manufactured by Hoya Corp.) 4 having a thickness of 1mm. In addition, a quartz glass 6 having a thickness of 1 mm was placedon the ITO fine-particle dispersion material 5 with the spacer 7provided therebetween so as to extend the ITO fine-particle dispersionmaterial 5 by pressure application. The structure thus formed wasirradiated by a high pressure mercury lamp (UL750, manufactured by HoyaCandeo Optronics Corp.) at 20 mW/cm² (illuminance through the quartzglass, illuminance meter: UIT-250, light receiving portion: UVD-5365)for 1,300 seconds (26 J), so that a measurement sample was cured. Afterthe curing was performed, a heat treatment was performed at 80° C. for72 hours.

Subsequently, as the post light irradiation from a quartz glass 6 side,light irradiation was performed using a high pressure mercury lamp 8(UL750, manufactured by Hoya Candeo Optronics Corp.) as shown in FIG. 3Athrough the quartz glass 6 by adjusting the illuminance so that theenergy at a wavelength of 300 to 400 nm was 100 J (40 mW, 2,500seconds).

The illuminance was determined by measuring light of the high pressuremercury lamp (UL750, manufactured by Hoya Candeo Optronics Corp.) in arange of 250 to 700 nm at 1 nm intervals through the quartz glass 6 by aspectral radiometer (USR-45D-13, manufactured by Ushio Inc.). The datais shown in FIG. 4A.

An accumulated value in a range of 300 to 350 nm was 17.3 mW, anaccumulated value in a range of 350 to 400 nm was 22.7 mW, and the totalwas 40 mW.

The ratio of the accumulated value in a range of 300 to 350 nm to thetotal accumulated value in a range of 300 to 400 nm was 43.4%.

Accordingly, the optical element 200 for refractive index measurementwas obtained. In FIG. 2B, the optical element 200 for refractive indexmeasurement is shown.

Example 2 <Formation of Optical Element 210 for Refractive IndexMeasurement>

An optical element 210 for refractive index measurement was formed asdescribed below.

Preceding steps before the post light irradiation were the same as thoseof the optical element 200 for refractive index measurement.

After annealing was performed at 80° C. for 72 hours, as the post lightirradiation from a quartz glass 6 side, light irradiation was performedusing a high pressure mercury lamp (UL750, manufactured by Hoya CandeoOptronics Corp.) as shown in FIG. 3B through a S-TIH11 glass substrate 9by adjusting the illuminance so that the energy at a wavelength of 300to 400 nm was 100 J (13.2 mW, 7,576 seconds).

The illuminance was determined by measuring light of the high pressuremercury lamp (UL750, manufactured by Hoya Candeo Optronics Corp.) in arange of 250 to 700 nm at 1 nm intervals through the S-TIH11 glasssubstrate 9 by a spectral radiometer (USR-45D-13, manufactured by UshioInc.). The data is shown in FIG. 4B.

An accumulated value in a range of 300 to 350 nm was 0.05 mW, anaccumulated value in a range of 350 to 400 nm was 13.15 mW, and thetotal was 13.2 mW.

The ratio of the accumulated value in a range of 300 to 350 nm to thetotal accumulated value in a range of 300 to 400 nm was 0.4%.

Accordingly, the optical element 210 for refractive index measurementwas obtained. In FIG. 2B, the optical element 210 for refractive indexmeasurement is shown (the structure is the same as that of the opticalelement 200 for refractive index measurement).

Example 3 <Formation of Optical Element 300 for Refractive IndexMeasurement>

An optical element 300 for refractive index measurement was formed asdescribed below.

First, as shown in FIG. 5A, a spacer 7 having a thickness of 12.5 μm andan ITO fine-particle dispersion material 5 (low refractive index andhigh dispersion material 11) were arranged on a high refractive indexglass (S-TIH11: manufactured by Hoya Corp.) 4 having a thickness of 1mm. In addition, a quartz glass 6 having a thickness of 1 mm was placedon the ITO fine-particle dispersion material 5 with the spacer 7provided therebetween so as to extend the ITO fine-particle dispersionmaterial 5 by pressure application. The structure thus formed wasirradiated by a high pressure mercury lamp (UL750, manufactured by HoyaCandeo Optronics Corp.) at 20 mW/cm² (illuminance through the quartzglass, illuminance meter: UIT-250, light receiving portion: UVD-5365)for 1,300 seconds (26 J), so that the ITO fine-particle dispersionmaterial 5 was cured. After the curing was performed, the quartz glass 6was peeled away, and annealing was performed at 80° C. for 72 hours.Subsequently, a spacer 11 having a thickness of 50 μm and a highrefractive index material 10 (high refractive index and low dispersionmaterial 21) were arranged as shown in FIG. 5B, and the quartz glass 6having a thickness of 1 mm was provided on the structure thus formedwith the spacer 11 interposed therebetween to extend the high refractiveindex material 10 by pressure application. As a result, as shown in FIG.5E, the structure was formed in which an oxygen block layer of the highrefractive index material 10 having a length of 300 μm from an airinterface to the ITO fine-particle dispersion material 5 and an oxygenabsorption layer of the high refractive index material 10 on the ITOfine-particle dispersion material 5 were provided. Next, the structureas described above was irradiated by a high pressure mercury lamp(UL750, manufactured by Hoya Candeo Optronics Corp.) at 20 mW/cm²(illuminance through the quartz glass, illuminance meter: UIT-250, lightreceiving portion: UVD-S365) for 1,300 seconds (26 J), so that the highrefractive index material 10 was cured. After the curing was performed,annealing was performed at 80° C. for 72 hours. Next, as shown in FIG.5C, as the post light irradiation from a quartz glass 6 side, lightirradiation was performed using a high pressure mercury lamp 8 (UL750,manufactured by Hoya Candeo Optronics Corp.) through the quartz glass 6by adjusting the illuminance so that the energy at a wavelength of 300to 400 nm was 100 J (40 mW, 2,500 seconds).

The illuminance was determined by measuring light of the high pressuremercury lamp (UL750, manufactured by Hoya Candeo Optronics Corp.) in arange of 250 to 700 nm at 1 nm intervals through the quartz glass 6 by aspectral radiometer (USR-45D-13, manufactured by Ushio Inc.). The datais shown in FIG. 4A.

An accumulated value in a range of 300 to 350 nm was 17.3 mW, anaccumulated value in a range of 350 to 400 nm was 22.7 mW, and the totalwas 40 mW.

Accordingly, the optical element 300 for refractive index measurementwas obtained. In FIG. 5E, the structure of the optical element 300 forrefractive index measurement is shown.

Example 4 <Formation of Optical Element 310 for Refractive IndexMeasurement>

An optical element 310 for refractive index measurement was formed asdescribed below.

Preceding steps before the post light irradiation were the same as thoseof the optical element 300 for refractive index measurement.

After annealing was performed at 80° C. for 72 hours, as shown in FIG.5C, as the post light irradiation from a quartz glass 6 side, lightirradiation was performed using a high pressure mercury lamp 8 (UL750,manufactured by Hoya Candeo Optronics Corp.) through the quartz glass 6by adjusting the illuminance so that the energy at a wavelength of 300to 400 nm was 50 J (40 mW, 1,250 seconds).

The illuminance was determined by measuring light of the high pressuremercury lamp 8 (UL750, manufactured by Hoya Candeo Optronics Corp.) in arange of 250 to 700 nm at 1 nm intervals through the quartz glass 6 by aspectral radiometer (USR-45D-13, manufactured by Ushio Inc.). The datais shown in FIG. 4A.

An accumulated value in a range of 300 to 350 nm was 17.3 mW, anaccumulated value in a range of 350 to 400 nm was 22.7 mW, and the totalwas 40 mW.

The ratio of the accumulated value in a range of 300 to 350 nm to thetotal accumulated value in a range of 300 to 400 nm was 43.4%.

Accordingly, the optical element 310 for refractive index measurementwas obtained. In FIG. 5E, the structure of the optical element 310 forrefractive index measurement is shown (the structure is the same as thatof the optical element 300 for refractive index measurement).

Example 5 <Formation of Optical Element 320 for Refractive IndexMeasurement>

An optical element 320 for refractive index measurement was formed asdescribed below.

Preceding steps before the post light irradiation were the same as thoseof the optical element 300 for refractive index measurement.

After annealing was performed at 80° C. for 72 hours, as the post lightirradiation from a quartz glass 6 side, light irradiation was performedusing a high pressure mercury lamp 8 (UL750, manufactured by Hoya CandeoOptronics Corp.) through a S-TIH11 glass substrate 9 as shown in FIG. 5Dby adjusting the illuminance so that the energy at a wavelength of 300to 400 nm was 100 J (13.2 mW, 7,576 seconds).

The illuminance was determined by measuring light of the high pressuremercury lamp 8 (UL750, manufactured by Hoya Candeo Optronics Corp.) in arange of 250 to 700 nm at 1 nm intervals through the S-TIH11 glasssubstrate 9 by a spectral radiometer (USR-45D-13, manufactured by UshioInc.). The data is shown in FIG. 4B.

An accumulated value in a range of 300 to 350 nm was 0.05 mW, anaccumulated value in a range of 350 to 400 nm was 13.15 mW, and thetotal was 13.2 mW.

The ratio of the accumulated value in a range of 300 to 350 nm to thetotal accumulated value in a range of 300 to 400 nm was 0.4%.

Accordingly, the optical element 320 for refractive index measurementwas obtained. In FIG. 5E, the structure of the optical element 320 forrefractive index measurement is shown (the structure is the same as thatof the optical element 300 for refractive index measurement).

Example 6 <Formation of Optical Element 330 for Refractive IndexMeasurement>

An optical element 330 for refractive index measurement was formed asdescribed below.

Preceding steps before the post light irradiation were the same as thoseof the optical element 300 for refractive index measurement.

After annealing was performed at 80° C. for 72 hours, as the post lightirradiation from a quartz glass 6 side, light irradiation was performedusing a high pressure mercury lamp 8 (UL750, manufactured by Hoya CandeoOptronics Corp.) through a S-TIH11 glass substrate 9 as shown in FIG. 5Dby adjusting the illuminance so that the energy at a wavelength of 300to 400 nm was 50 J (13.2 mW, 3,788 seconds).

The illuminance was determined by measuring light of the high pressuremercury lamp 8 (UL750, manufactured by Hoya Candeo Optronics Corp.) in arange of 250 to 700 nm at 1 nm intervals through the S-TIH11 glasssubstrate 9 by a spectral radiometer (USR-45D-13, manufactured by UshioInc.). The data is shown in FIG. 4B. FIG. 4B is a spectrum of the highpressure mercury lamp for the optical element of the example accordingto aspects of the present invention through the S-TIH11 glass substrate.

An accumulated value in a range of 300 to 350 nm was 0.05 mW, anaccumulated value in a range of 350 to 400 nm was 13.15 mW, and thetotal was 13.2 mW.

The ratio of the accumulated value in a range of 300 to 350 nm to thetotal accumulated value in a range of 300 to 400 nm was 0.4%.

Accordingly, the optical element 330 for refractive index measurementwas obtained. In FIG. 5E, the structure of the optical element 330 forrefractive index measurement is shown (the structure is the same as thatof the optical element 300 for refractive index measurement).

Example 10 <Formation of Optical Element 500 for Refractive IndexMeasurement>

An optical element 500 for refractive index measurement was formed asdescribed below.

First, as shown in FIG. 9A, a spacer 7 having a thickness of 12.5 μm andan ITO fine-particle dispersion material 5 (low refractive index andhigh dispersion material 11) were arranged on a high refractive indexglass (S-TIH11: manufactured by Hoya Corp.) 4 having a thickness of 1mm. In addition, a quartz glass 6 having a thickness of 1 mm was placedon the ITO fine-particle dispersion material 5 with the spacer 7provided therebetween so as to extend the ITO fine-particle dispersionmaterial 5 by pressure application. The structure thus formed wasirradiated by a high pressure mercury lamp (UL750, manufactured by HoyaCandeo Optronics Corp.) at 20 mW/cm² (illuminance through the quartzglass, illuminance meter: UIT-250, light receiving portion: UVD-5365)for 1,300 seconds (26 J), so that the ITO fine-particle dispersionmaterial 5 was cured. After the curing was performed, the quartz glass 6was peeled away, and annealing was performed at 80° C. for 72 hours.Subsequently, a high refractive index material 10 (high refractive indexand low dispersion material 21) was arranged as shown in FIG. 9B, andthe quartz glass 6 having a thickness of 1 mm was provided on thestructure formed as described above to extend the high refractive indexmaterial 10 by pressure application. As a result, as shown in FIG. 9E,the structure was formed in which an oxygen block layer of the highrefractive index material 10 having a length of 300 μm from an airinterface to the ITO fine-particle dispersion material 5 was provided.Next, the structure as described above was irradiated by a high pressuremercury lamp (UL750, manufactured by Hoya Candeo Optronics Corp.) at 20mW/cm² (illuminance through the quartz glass, illuminance meter:UIT-250, light receiving portion: UVD-S365) for 1,300 seconds (26 J), sothat the high refractive index material 10 was cured. After the curingwas performed, annealing was performed at 80° C. for 72 hours. Next, asshown in FIG. 9C, as the post light irradiation from a quartz glass 6side, light irradiation was performed using a high pressure mercury lamp8 (UL750, manufactured by Hoya Candeo Optronics Corp.) through thequartz glass 6 by adjusting the illuminance so that the energy at awavelength of 300 to 400 nm was 100 J (40 mW, 2,500 seconds).

The illuminance was determined by measuring light of the high pressuremercury lamp (UL750, manufactured by Hoya Candeo Optronics Corp.) in arange of 250 to 700 nm at 1 nm intervals through the quartz glass 6 by aspectral radiometer (USR-45D-13, manufactured by Ushio Inc.). The datais shown in FIG. 4A.

An accumulated value in a range of 300 to 350 nm was 17.3 mW, anaccumulated value in a range of 350 to 400 nm was 22.7 mW, and the totalwas 40 mW.

Accordingly, the optical element 500 for refractive index measurementwas obtained. In FIG. 9E, the structure of the optical element 500 forrefractive index measurement is shown.

Example 11 <Formation of Optical Element 510 for Refractive IndexMeasurement>

An optical element 510 for refractive index measurement was formed asdescribed below.

Preceding steps before the post light irradiation were the same as thoseof the optical element 500 for refractive index measurement.

After annealing was performed at 80° C. for 72 hours, as the post lightirradiation from a quartz glass 6 side, light irradiation was performedusing a high pressure mercury lamp 8 (UL750, manufactured by Hoya CandeoOptronics Corp.) through a S-TIH11 glass substrate 9 as shown in FIG. 9Dby adjusting the illuminance so that the energy at a wavelength of 300to 400 nm was 100 J (13.2 mW, 7,576 seconds).

The illuminance was determined by measuring light of the high pressuremercury lamp 8 (UL750, manufactured by Hoya Candeo Optronics Corp.) in arange of 250 to 700 nm at 1 nm intervals through the S-TIH11 glasssubstrate 9 by a spectral radiometer (USR-45D-13, manufactured by UshioInc.). The data is shown in FIG. 4B.

An accumulated value in a range of 300 to 350 nm was 0.05 mW, anaccumulated value in a range of 350 to 400 nm was 13.15 mW, and thetotal was 13.2 mW.

The ratio of the accumulated value in a range of 300 to 350 nm to thetotal accumulated value in a range of 300 to 400 nm was 0.4%.

Accordingly, the optical element 510 for refractive index measurementwas obtained. In FIG. 9E, the structure of the optical element 510 forrefractive index measurement is shown (the structure is the same as thatof the optical element 500 for refractive index measurement).

[Evaluation of Optical Properties (Refractive Indices) of OpticalElements 200, 210, 300, 310, 320, 330, 500, and 510 for Refractive IndexMeasurement]

By using a refractometer (KPR-30, manufactured by Shimadzu Corp.), therefractive indices at the g line (435.8 nm), the f line (486.1 nm), thee line (546.1 nm), the d line (587.6 nm), and the c line (656.3 nm) ofeach cured sample were measured from a high refractive index glass 4side. In addition, from the measured refractive index, the Abbe's numberwas calculated.

<Multilayer Diffractive Optical Element>

Next, after a diffractive optical shape was formed using the lowrefractive index and high dispersion material 11, the high refractiveindex and low dispersion material 21 was laminated thereon withoutforming any space therebetween to form a multilayer diffractive opticalelement, and the evaluation thereof was then performed.

Example 12 <Formation of Multilayer Diffractive Optical Element 400>

First, as shown in FIG. 6A, an ITO fine-particle dispersion material 5(low refractive index and high dispersion material 11) and a glasssubstrate (hereinafter referred to as “flat glass plate” in some cases)13 having a thickness of 2 mm were provided in this order on a mold 12having a diffraction grating shape. After curing was performed by lightirradiation using a high pressure mercury lamp (EXECURE250, Hoya CandeOptronics Corp.) at 14.2 mW/cm² for 211 seconds and at 20 mW/cm² for 600seconds (illuminance through the glass substrate 13, illuminance meter:UIT-250, light receiving portion: UVD-S365), as shown in FIG. 6B, theITO fine-particle dispersion material 5 was removed from the mold.Subsequently, annealing was performed in the air at 80° C. for 72 hours,so that a diffraction grating was formed. The grating height of thediffraction grating measured after the annealing was 10.8 μm, thedistance from the glass substrate 13 to the valley of the grating was 2μm (the average thickness of the ITO fine-particle dispersion material 5was 7.4 μm), and the pitch was 80 μm.

Next, the ITO fine-particle dispersion material 5 molded on the flatglass plate 13 was set together therewith in a molding jig 15, and onthe ITO fine-particle dispersion material 5, a high refractive indexmaterial 10 (high refractive index and low dispersion material 21) wasdripped (FIG. 7A). Another flat glass plate 13 was provided thereon(FIG. 7B) to extend the high refractive index material 10 by pressureapplication, so that as shown in FIG. 7C, the structure was formed inwhich an oxygen block layer of the high refractive index material 10having a length of 300 μm from an air interface to the ITO fine-particledispersion material 5 and a 35 μm-thick oxygen absorption layer of thehigh refractive index material 10 having a height larger than that ofthe grating of the ITO fine-particle dispersion material 5 wereprovided. After the sample thus prepared was cured by light irradiationusing a high pressure mercury lamp (EXECURE250, Hoya Cande OptronicsCorp.) at 14.2 mW/cm² for 211 seconds and at 20 mW/cm² for 600 seconds(illuminance through the flat glass plate 13, illuminance meter:UIT-250, light receiving portion: UVD-S365), annealing was performed at80° C. for 72 hours.

Subsequently, as the post light irradiation from a flat glass plate 13side, light irradiation was performed using a high pressure mercury lamp8 (UL750, manufactured by Hoya Candeo Optronics Corp.) through the flatglass plate 13 as shown in FIG. 7D by adjusting the illuminance so thatthe energy at a wavelength of 300 to 400 nm was 100 J (42 mW, 2,381seconds).

The illuminance was determined by measuring light of the high pressuremercury lamp (UL750, manufactured by Hoya Candeo Optronics Corp.) in arange of 250 to 700 nm at 1 nm intervals through the flat glass plate 13by a spectral radiometer (USR-45D-13, manufactured by Ushio Inc.). Thedata is shown in FIG. 4A.

An accumulated value in a range of 300 to 350 nm was 14.4 mW, anaccumulated value in a range of 350 to 400 nm was 25.6 mW, and the totalwas 40 mW.

The ratio of the accumulated value in a range of 300 to 350 nm to thetotal accumulated value in a range of 300 to 400 nm was 36.1%.

Accordingly, a multilayer diffractive optical element 400 was obtained.In FIG. 7C, the structure of the optical element 400 for refractiveindex measurement is shown.

Example 13 <Formation of Multilayer Diffractive Optical Element 410>

A multilayer diffractive optical element 410 was formed as describedbelow.

Preceding steps before the post light irradiation were the same as thoseof the multilayer diffractive optical element 400.

After annealing was performed at 80° C. for 72 hours, as the post lightirradiation from a flat glass plate 13 side, light irradiation wasperformed using a high pressure mercury lamp 8 (UL750, manufactured byHoya Candeo Optronics Corp.) through a S-TIH11 glass substrate 9 asshown in FIG. 7E by adjusting the illuminance so that the energy at awavelength of 300 to 400 nm was 100 J (13.9 mW, 7,194 seconds).

The illuminance was determined by measuring light of the high pressuremercury lamp (UL750, manufactured by Hoya Candeo Optronics Corp.) in arange of 250 to 700 nm at 1 nm intervals through the S-TIH11 glasssubstrate 9 by a spectral radiometer (USR-45D-13, manufactured by UshioInc.). The data is shown in FIG. 4B.

An accumulated value in a range of 300 to 350 nm was 0.05 mW, anaccumulated value in a range of 350 to 400 nm was 13.15 mW, and thetotal was 13.2 mW.

The ratio of the accumulated value in a range of 300 to 350 nm to thetotal accumulated value in a range of 300 to 400 nm was 0.4%.

Accordingly, the multilayer diffractive optical element 410 wasobtained. In FIG. 7C, the multilayer diffractive optical element 410 isshown (the structure is the same as that of the multilayer diffractiveoptical element 400).

<Evaluation of Diffraction Efficiency>

As for the diffraction efficiency, after spot light was made incident onthe above multilayer diffractive optical element, and the amount of thewhole transmitted light passing therethrough was measured by a lightreceiving portion in close contact with the element, the amount of lightof the design order (first-order diffracted light) was measured, and theratio in the amount of light (amount of light of design order/amount ofwhole transmitted light) was defined as the diffraction efficiency.

<Evaluation of Light Resistance>

For the optical elements 200, 210, 300, 310, 320, 330, 500, and 510 forrefractive index measurement and the multilayer diffractive opticalelements 400 and 410, a light resistance test was performed at 5 mW(irradiation intensity at 300 to 400 nm) for 200 hours using a lightresistance tester (xenon weather meter X75, manufactured by Suga TestInstruments Co., Ltd.).

In this test, the light incident on each sample was light passingthrough a 390-nm cut filter (actually light leakage occurred to 360 nm).FIG. 8 shows a spectrum of a xenon arc lamp through a 390-nm cut filter.The irradiation intensity through a 390-nm cut filter was 0.8 mW(irradiation intensity at a wavelength of 300 to 400 nm).

Subsequently, the refractive index of the optical element for refractiveindex measurement and the diffraction efficiency of the multilayerdiffractive optical element were measured.

<Measurement of Oxygen Permeability and Solubility of Material>

As shown in FIG. 9A, on a quartz glass 4 having a thickness of 1 mm, aspacer 7 having a thickness of 100 μm and an ITO fine-particledispersion material 5 (low refractive index and high dispersion material11) or a high refractive index material 10 (high refractive index andlow dispersion material 21) were arranged. A quartz glass 6 having athickness of 1 mm was further provided thereon with the spacer 7provided therebetween, so that the ITO fine-particle dispersion material5 (low refractive index and high dispersion material 11) or the highrefractive index material 10 (high refractive index and low dispersionmaterial 21) was extended by pressure application. The structure thusformed was irradiated by a high pressure mercury lamp (UL750,manufactured by Hoya Candeo Optronics Corp.) at 20 mW/cm² (illuminancethrough the quartz glass, illuminance meter: UIT-250, light receivingportion: UVD-S365) for 1,300 seconds (26 J), so that a measurementmaterial was cured. After the curing was performed, the film was peeledaway from the quartz glasses, and a heat treatment was performed at 80°C. for 72 hours.

The oxygen permeability and the oxygen solubility of the film formed asdescribed above were measured using a differential pressure type gaspermeability measurement device (GTR-30XATR, manufactured by GTR TecCorp.) at 23±2° C. (also at 50±2° C. and 80±2° C. for accelerationfactor conversion for subsequent acceleration tests).

However, when the oxygen permeability of the optical element 210 forrefractive index measurement obtained by the differential pressure typegas permeability measurement is compared with a travel distance ofoxygen in the actual optical element 210 for refractive indexmeasurement, the oxygen permeability of the actual optical element 210for refractive index measurement estimated from the travel distance ofoxygen is approximately 100 times the oxygen permeability obtained bythe differential pressure type gas permeability measurement.Accordingly, although the oxygen permeability obtained by thedifferential pressure type gas permeability measurement indicatesrelative oxygen permeability and oxygen solubility between the films,when the oxygen diffusion behavior in the actual film is considered, theabove permeability must be regarded as one hundredth thereof forcalculation.

<Change with Time (Measurement by Oxidation Acceleration Device)>

The progress of oxidation was defined by the travel distance ofoxidation from the end portion of the optical element to the boundary ofdiscoloration of the ITO fine-particle dispersion material 5 (lowrefractive index and high dispersion material 11).

The travel distance of oxidation of a sample of the optical element 210for refractive index measurement which was left for 365 days was 3 mm.On the other hand, when an oxidation acceleration device was formed(oxygen concentration: 100%, 6 atmospheric pressure, 60° C.), and theoptical element 210 for refractive index measurement was left thereinfor 66 hours, the travel distance of oxidation was also 3 mm.

The acceleration factor was 132 times. In addition, since theacceleration factor theoretically obtained from 5 times the oxygenconcentration (100%−20%)×6 times the pressure (6 atm←1 atm)×temperaturecoefficient of permeability (4.30=P(60° C.)/P(23° C.)) was 129 times andwas coincide with the measured acceleration factor, the accelerationfactors of the other materials were also theoretically obtained, and thetimes thereof were obtained.

In this case, the element was placed in the oxidation accelerationdevice for 72 hours.

When the element was formed only from the ITO fine-particle dispersionmaterial 5 (low refractive index and high dispersion material 11), thecorresponding time was 25.4 years by calculation, and when the oxygenblock layer of the high refractive index material 10 having a length of300 μm to the ITO fine-particle dispersion material 5 was formed, thecorresponding time was 24.6 years by calculation. Hence, the test resultobtained in this case was regarded to correspond to that obtained whenthe sample was left for 25 years under common use conditions.

<Evaluation Results> Initial Evaluation Results

The multilayer diffractive optical elements 400 and 410 each formed fromthe low refractive index and high dispersion material 11 and the highrefractive index and low dispersion material 21 had a diffractionefficiency of 99.5% or more in the whole visible region.

The low refractive index and high dispersion material 11 of the opticalelement 200 for refractive index measurement had refractive indices(n_(g), n_(f), n_(e), n_(d), n_(C))=(1.599, 1.586, 1.575, 1.567, 1.556)and (ν_(d), θ_(gF))=(18.6, 0.41).

The low refractive index and high dispersion material 11 of the opticalelement 210 for refractive index measurement had refractive indices(n_(g), n_(f), n_(e), n_(d), n_(C))=(1.599, 1.587, 1.575, 1.568, 1.557)and (ν_(d), θ_(gF))=(18.9, 0.41).

The low refractive index and high dispersion material 11 of the opticalelement 300 for refractive index measurement had refractive indices(n_(g), n_(f), n_(e), n_(d), n_(C))=(1.600, 1.588, 1.576, 1.568, 1.557),and (ν_(d), θ_(gF))=(18.8, 0.40) is obtained.

The low refractive index and high dispersion material 11 of the opticalelement 310 for refractive index measurement had refractive indices(n_(g), n_(f), n_(e), n_(d), n_(C))=(1.600, 1.587, 1.576, 1.568, 1.557)and (ν_(d), θ_(gF))=(19.0, 0.42).

The low refractive index and high dispersion material 11 of the opticalelement 320 for refractive index measurement had refractive indices(n_(g), n_(f), n_(e), n_(d), n_(C))=(1.600, 1.588, 1.577, 1.569, 1.558)and (ν_(d), θ_(gF))=(19.1, 0.41).

The low refractive index and high dispersion material 11 of the opticalelement 330 for refractive index measurement had refractive indices(n_(g), n_(f), n_(e), n_(d), n_(C))=(1.600, 1.588, 1.576, 1.569, 1.558)and (ν_(d), θ_(gF))=(19.21, 0.42).

<Results of Oxygen Permeability and Solubility of Material>

Hereinafter, “E” indicates an exponential function with 10 as the base.

The low refractive index and high dispersion material 11 had (oxygenpermeability P/cm³·cm·(cm²·s·cmHg)⁻¹, oxygen solubilityS/cm³(cm³·cmHg)⁻¹)=(4.06E⁻¹¹, 1.4E⁻³).

The high refractive index and low dispersion material 21 had (oxygenpermeability P/cm³·cm·(cm²·s·cmHg)⁻¹, oxygen solubilityS/cm³(cm³·cmHg)⁻¹)=(8.58E⁻¹², 3.3E⁻³).

The results of light resistance obtained by the light resistance testare shown in Table 1.

TABLE 1 OXYGEN PERMEATION INHIBITION/OXYGEN ABSORPTION ELEMENT STRUCTUREMATERIAL PROPERTIES OXYGEN OXYGEN OPTICAL TYPE OF PERMEATIONPERMEABILITY OXYGEN ELEMENT OPTICAL INHIBITION OXYGEN P/cm3 · cm · (cm2· SOLUBILITY NO. ELEMENT LAYER ABSORPTION s · cmHg) − 1 S/cm3 · (cm3 ·cmHg) − 1 EXAMPLE 1 200 REFRACTIVE NO NO INDEX SAMPLE EXAMPLE 2 210REFRACTIVE NO NO INDEX SAMPLE COMPARATIVE 220 REFRACTIVE NO NO EXAMPLE 1INDEX SAMPLE EXAMPLE 3 300 REFRACTIVE 300 μm 37 μm 8.58E−12 3.3E−03INDEX SAMPLE EXAMPLE 4 310 REFRACTIVE 300 μm 37 μm 8.58E−12 3.3E−03INDEX SAMPLE EXAMPLE 5 320 REFRACTIVE 300 μm 37 μm 8.58E−12 3.3E−03INDEX SAMPLE EXAMPLE 6 330 REFRACTIVE 300 μm 37 μm 8.58E−12 3.3E−03INDEX SAMPLE EXAMPLE 7 340 REFRACTIVE 300 μm 37 μm 8.58E−12 3.3E−03INDEX SAMPLE EXAMPLE 8 350 REFRACTIVE 300 μm 37 μm 4.06E−11 1.4E−03INDEX SAMPLE EXAMPLE 9 360 REFRACTIVE 300 μm 37 μm 4.06E−11 1.4E−03INDEX SAMPLE COMPARATIVE 370 REFRACTIVE 300 μm 37 μm 4.06E−11 1.4E−03EXAMPLE 2 INDEX SAMPLE EXAMPLE 10 500 REFRACTIVE 300 μm NO 8.58E−123.3E−03 INDEX SAMPLE EXAMPLE 11 510 REFRACTIVE 300 μm NO 8.58E−123.3E−03 INDEX SAMPLE EXAMPLE 12 400 DIFFRACTIVE 300 μm 35 μm 8.58E−123.3E−03 OPTICAL ELEMENT EXAMPLE 13 410 DIFFRACTIVE 300 μm 35 μm 8.58E−123.3E−03 OPTICAL ELEMENT EXAMPLE 14 420 DIFFRACTIVE 300 μm 35 μm 8.58E−123.3E−03 OPTICAL ELEMENT COMPARATIVE 430 DIFFRACTIVE 300 μm 35 μm4.06E−11 1.4E−03 EXAMPLE 3 OPTICAL ELEMENT ENVIRONMENTAL DURABILITY TESTLIGHT RESISTANCE OXIDATION ACCELERATION TEST TEST CHANGE IN CHANGE INREFRACTIVE REFRACTIVE INDEX INDEX POST LIGHT IRRADIATION STEP TRAVELΔn(CHANGE IN Δn(CHANGE IN EXCESSIVE DISTANCE DIFFRACTION DIFFRACTIONLIGHT OF EFFICIENCY OF EFFICIENCY OF POST LIGHT IRRADIATION OXIDATIONDIFFRACTION DIFFRACTION EXECUTION IRRADIATION (300-350 cut) RANK (mm)GRATING) RANK GRATING) EXAMPLE 1 YES 100J — C 15.3 0.004 A 0.000 EXAMPLE2 YES — 100J C 15.3 0.003 A −0.001 COMPARATIVE NO — — C 15.3 0.002 B−0.002 EXAMPLE 1 EXAMPLE 3 YES 100J — A 2.3 A 0.000 EXAMPLE 4 YES  50J —A 2.3 A 0.000 EXAMPLE 5 YES — 100J A 2.3 A −0.001 EXAMPLE 6 YES —  50J A2.3 A −0.001 EXAMPLE 7 NO — — A 2.3 B −0.002 EXAMPLE 8 YES 100J — C 15.30.004 A 0.000 EXAMPLE 9 YES — 100J C 15.3 0.003 A −0.001 COMPARATIVE NO— — C 15.3 0.002 B −0.002 EXAMPLE 2 EXAMPLE 10 YES 100J — B 5.5 A 0.000EXAMPLE 11 YES — 100J B 5.5 A −0.001 EXAMPLE 12 YES 100J — A 2.2 0.0 A0.0 EXAMPLE 13 YES — 100J A 2.2 0.0 A 0.0 EXAMPLE 14 NO — — A 2.2 0.0 B−0.7 COMPARATIVE NO — — C 15.3 −0.7 B −0.7 EXAMPLE 3

When the change in the diffraction efficiency was 0.5% or less, or thechange in the refractive index was less than 0.002 as the result of thelight resistance, it was ranked as A, and when the change in thediffraction efficiency was more than 0.5%, or the change in therefractive index was 0.002 or more, it was ranked as B. In the case ofthe multilayer diffractive optical elements 400 and 410 each formed fromthe low refractive index and high dispersion material 11 and the highrefractive index and low dispersion material 21, the diffractionefficiency in the whole visible region was 99.5% or more and was not somuch changed from the initial value.

(Refractive Index and Optical Constant)

Since the low refractive index and high dispersion material 11 of theoptical element 200 for refractive index measurement had refractiveindices (n_(g), n_(f), n_(e), n_(d), n_(C))=(1.599, 1.586, 1.575, 1.567,1.556) and (ν_(d), θ_(gF))=(18.6, 0.41), the change in the refractiveindex from the initial value was hardly observed.

Since the low refractive index and high dispersion material 11 of theoptical element 210 for refractive index measurement had refractiveindices (n_(g), n_(f), n_(e), n_(d), n_(C))=(1.599, 1.586, 1.575, 1.567,1.556) and (ν_(d), θ_(gF))=(18.7, 0.41), the change in the refractiveindex from the initial value was from 0.000 to −0.0010.

Since the low refractive index and high dispersion material 11 of theoptical element 300 for refractive index measurement had refractiveindices (n_(g), n_(f), n_(e), n_(d), n_(C))=(1.600, 1.587, 1.576, 1.568,1.557) and (ν_(d), θ_(gF))=(18.71, 0.41), the change in the refractiveindex from the initial value was hardly observed.

Since the low refractive index and high dispersion material 11 of theoptical element 310 for refractive index measurement had refractiveindices (n_(g), n_(f), n_(e), n_(d), n_(C))=(1.600, 1.588, 1.576, 1.568,1.557) and (ν_(d), θ_(gF))=(18.6, 0.40), the change in the refractiveindex from the initial value was hardly observed.

Since the low refractive index and high dispersion material 11 of theoptical element 320 for refractive index measurement had refractiveindices (n_(g), n_(f), n_(e), n_(d), n_(C))=(1.600, 1.587, 1.576, 1.568,1.557) and (ν_(d), θ_(gF))=(18.9, 0.41), the change in the refractiveindex from the initial value was from 0.000 to −0.0010.

Since the low refractive index and high dispersion material 11 of theoptical element 330 for refractive index measurement had refractiveindices (n_(g), n_(f), n_(e), n_(d), n_(C))=(1.600, 1.587, 1.576, 1.568,1.557) and (ν_(d), θ_(gF))=(18.7, 0.40), the change in the refractiveindex from the initial value was from 0.000 to −0.001.

The low refractive index and high dispersion material 11 of the opticalelement 500 for refractive index measurement had refractive indices(n_(g), n_(f), n_(e), n_(d), n_(C))=(1.600, 1.588, 1.576, 1.568, 1.557)and (ν_(d), θ_(gF))=(18.8, 0.40).

The low refractive index and high dispersion material 11 of the opticalelement 510 for refractive index measurement had refractive indices(n_(g), n_(f), n_(e), n_(d), n_(C))=(1.600, 1.588, 1.577, 1.569, 1.558)and (ν_(d), θ_(gF))=(19.1, 0.41).

<Results of Oxidation Acceleration Test> (Travel Speed of Oxidation,Refractive Index, and Optical Constant)

The results of an oxidation acceleration test are shown in Table 1.

A travel distance of oxidation of 2.5 mm or less (2.5 mm) was ranked asA, a travel distance in a range of more than 2.5 to 10 mm was ranked asB, and a travel distance of more than 10 mm was ranked as C.

In the optical element 200 for refractive index measurement, the traveldistance of oxidation from the end portion was 15.3 mm which was largerthan a width of 2.5 mm of an annular zone located around an effectivediameter zone (hereinafter simply referred to as “the width of 2.5 mm ofthe annular zone” in some cases) and was extended in the effectivediameter zone by 12.8 mm.

An oxidized portion of the low refractive index and high dispersionmaterial 11 had refractive indices (n_(g), n_(f), n_(e), n_(d),n_(C))=(1.600, 1.588, 1.578, 1.571, 1.560) and (ν_(d), θ_(gF))=(20.0,0.42), and the change in the refractive index from the initial value wasfrom +0.002 to +0.004 and was out of the acceptable range.

In the optical element 210 for refractive index measurement, the traveldistance of oxidation from the end portion was 15.3 mm which was largerthan the width of 2.5 mm of the annular zone and was extended in theeffective diameter zone by 12.8 mm.

The low refractive index and high dispersion material 11 had refractiveindices (n_(g), n_(f), n_(e), n_(d), n_(C))=(1.600, 1.588, 1.578, 1.571,1.560) and (ν_(d), θ_(gF))=(20.0, 0.42), and the change in therefractive index from the initial value was from +0.001 to +0.003 andwas out of the acceptable range.

The travel distance of oxidation from the end portion of the opticalelement 300 for refractive index measurement was 2.3 mm which was withinthe width of 2.5 mm of the annular zone. Since the end portion wassmall, the refractive index could not be measured.

The travel distance of oxidation from the end portion of the opticalelement 310 for refractive index measurement was 2.3 mm which was withinthe width of 2.5 mm of the annular zone. Since the end portion wassmall, the refractive index could not be measured.

The travel distance of oxidation from the end portion of the opticalelement 320 for refractive index measurement was 2.3 mm which was withinthe width of 2.5 mm of the annular zone. Since the end portion wassmall, the refractive index could not be measured.

The travel distance of oxidation from the end portion of the opticalelement 330 for refractive index measurement was 2.3 mm which was withinthe width of 2.5 mm of the annular zone. Since the end portion wassmall, the refractive index could not be measured.

The travel distance of oxidation from the end portion of the opticalelement 500 for refractive index measurement was 5.0 mm which was largerthan the width of 2.5 mm of the annular zone and was extended in theeffective diameter zone by 2.5 mm. Since the end portion was small, therefractive index could not be measured.

The travel distance of oxidation from the end portion of the opticalelement 510 for refractive index measurement was 5.0 mm which was largerthan the width of 2.5 mm of the annular zone and was extended in theeffective diameter zone by 2.5 mm. Since the end portion was small, therefractive index could not be measured.

The travel distance of oxidation from the end portion of the multilayerdiffractive optical element 400 was 2.3 mm which was within the width of2.5 mm of the annular zone. The change in the diffraction efficiency andinconveniences of the whole element were not observed.

The travel distance of oxidation from the end portion of the multilayerdiffractive optical element 410 was 2.3 mm which was within the width of2.5 mm of the annular zone. The change in the diffraction efficiency andinconveniences of the whole element were not observed.

Comparative Example 1

In Comparative Example 1, the post light irradiation was not performedon the element for refractive index measurement.

<Formation of Optical Element 220 for Refractive Index Measurement>

An optical element 220 for refractive index measurement had the samestructure as that of the optical element 200 or 210 for refractive indexmeasurement and was formed as described below without performing thepost light irradiation.

First, as shown in FIG. 2A, a spacer 7 having a thickness of 12.5 μm andan ITO fine-particle dispersion material 5 (low refractive index andhigh dispersion material 11) were arranged on a high refractive indexglass (S-TIH11: manufactured by Hoya Corp.) 4 having a thickness of 1mm. In addition, a quartz glass 6 having a thickness of 1 mm was placedon the ITO fine-particle dispersion material 5 with the spacer 7provided therebetween so as to extend the ITO fine-particle dispersionmaterial 5 by pressure application. The structure thus formed wasirradiated by a high pressure mercury lamp (UL750, manufactured by HoyaCandeo Optronics Corp.) at 20 mW/cm² (illuminance through the quartzglass, illuminance meter: UIT-250, light receiving portion: UVD-S365)for 1,300 seconds (26 J), so that a measurement sample was cured. Afterthe curing was performed, annealing was performed at 80° C. for 72hours.

Accordingly, the optical element 220 for refractive index measurementwas obtained. In FIG. 2B, the optical element 220 for refractive indexmeasurement is shown (the element structure is the same as that of theoptical element 200 for refractive index measurement).

Example 7 <Formation of Optical Element 340 for Refractive IndexMeasurement>

An optical element 340 for refractive index measurement was formed asdescribed below.

The optical element 340 for refractive index measurement had the samestructure as that of the optical element 300 for refractive indexmeasurement and was formed as described below without performing thepost light irradiation.

First, as shown in FIG. 5A, a spacer 7 having a thickness of 12.5 μm andan ITO fine-particle dispersion material 5 (low refractive index andhigh dispersion material 11) were arranged on a high refractive indexglass (S-TIH11: manufactured by Hoya Corp.) 4 having a thickness of 1mm. In addition, a quartz glass 6 having a thickness of 1 mm was placedon the ITO fine-particle dispersion material 5 with the spacer 7provided therebetween so as to extend the ITO fine-particle dispersionmaterial 5 by pressure application. The structure thus formed wasirradiated by a high pressure mercury lamp (UL750, manufactured by HoyaCandeo Optronics Corp.) at 20 mW/cm² (illuminance through the quartzglass, illuminance meter: UIT-250, light receiving portion: UVD-5365)for 1,300 seconds (26 J), so that the ITO fine-particle dispersionmaterial 5 was cured. After the curing was performed, the quartz glass 6was peeled away, and annealing was performed at 80° C. for 72 hours.Subsequently, a spacer 11 having a thickness of 50 μm and a highrefractive index material 10 (high refractive index and low dispersionmaterial 21) were arranged as shown in FIG. 5B, and the quartz glass 6having a thickness of 1 mm was provided on the structure formed asdescribed above with the spacer 11 interposed therebetween to extend thehigh refractive index material 10 by pressure application. As a result,as shown in FIG. 5E, the structure was formed in which an oxygen blocklayer of the high refractive index material 10 having a length of 300 μmfrom an air interface to the ITO fine-particle dispersion material 5 andan oxygen absorption layer of the high refractive index material 10 onthe ITO fine-particle dispersion material 5 were provided. Next, thestructure as described above was irradiated by a high pressure mercurylamp (UL750, manufactured by Hoya Candeo Optronics Corp.) at 20 mW/cm²(illuminance through the quartz glass, illuminance meter: UIT-250, lightreceiving portion: UVD-5365) for 1,300 seconds (26 J), so that the highrefractive index material 10 was cured. After the curing was performed,annealing was performed at 80° C. for 72 hours.

Accordingly, the optical element 340 for refractive index measurementwas obtained. In FIG. 5E, the structure of the optical element 340 forrefractive index measurement is shown (the structure is the same as thatof the optical element 300 for refractive index measurement).

[Preparation of High Refractive Index and Low Dispersion Material 22]

After a fine-particle dispersion liquid (average particle diameter offine particles: 10 nm, concentration of zirconium oxide: 10 percent byweight, no surface treatment agent, manufactured by Sumitomo OsakaCement Co., Ltd.) in which zirconium oxide was dispersed in a ethanolsolvent was processed by solvent displacement with acetone,DISPERBYK-163 (high molecular weight block copolymer, manufactured byBYK Japan KK) was added thereto as a dispersant, and solventdisplacement was then performed with toluene, so that a zirconium oxideliquid (concentration of zirconium oxide: 9.5 percent by weight,concentration of a surface treatment agent: 2.57 percent by weight) inwhich zirconium oxide was dispersed in a toluene solution was formed.

Next, 161.2 g of the zirconium oxide liquid formed as described abovewas mixed with 10.57 g of a mixture as an ultraviolet curable acrylicresin containing 20 percent by weight oftris(2-acryloxyethyl)isocyanurate, 25 percent by weight ofpentaerythritol triacrylate, 40 percent by weight of dicyclopentenyloxyethyl methacrylate, 13 percent by weight of a urethane modifiedpolyester acrylate, and 2 percent by weight of 1-hydroxycyclohexylphenyl ketone. This mixed solution was received in an evaporator, andtoluene was removed finally at an oil bath temperature of 45° C. and aset pressure of 2 hPas for 20 hours, so that a high refractive index andlow dispersion material 22 was prepared.

In addition, the particle diameter of zirconium oxide was measured by alaser type particle size analyzer (ELS, manufactured by OtsukaElectronics Co., Ltd.). Although the value submitted by Sumitomo OsakaCement Co., Ltd. was 3 to 5 nm, since the laser type particle sizedistribution was obtained by measuring particle diameters including thatof a surface treatment agent, it was estimated the data obtained therebywas different from the actual value.

In addition, by a TGA (manufactured by PerkinElmer), the high refractiveindex and low dispersion material 22 was fired, and the inorganic solidcomponent thereof was quantitatively determined, so that a content of53.7 percent by weight was obtained.

The content of a remaining solvent (toluene) measured by a gaschromatography (5890 series II, manufactured by Hewlett Packard) was0.005 percent by weight or less and was the detection limit or less.

Example 8 <Formation of Optical Element 350 for Refractive IndexMeasurement>

An optical element 350 for refractive index measurement was formed asdescribed below.

First, as shown in FIG. 5A, a spacer 7 having a thickness of 12.5 μm andan ITO fine-particle dispersion material 5 (low refractive index andhigh dispersion material 11) were arranged on a high refractive indexglass (S-TIH11: manufactured by Hoya Corp.) 4 having a thickness of 1mm. In addition, a quartz glass 6 having a thickness of 1 mm was placedon the ITO fine-particle dispersion material 5 with the spacer 7provided therebetween so as to extend the ITO fine-particle dispersionmaterial 5 by pressure application. The structure thus formed wasirradiated by a high pressure mercury lamp (UL750, manufactured by HoyaCandeo Optronics Corp.) at 20 mW/cm² (illuminance through the quartzglass, illuminance meter: UIT-250, light receiving portion: UVD-5365)for 1,300 seconds (26 J), so that the ITO fine-particle dispersionmaterial 5 was cured. After the curing was performed, the quartz glass 6was peeled away, and annealing was performed at 80° C. for 72 hours.Subsequently, after a spacer 11 having a thickness of 50 μm wasarranged, and unlike the case of the optical element 300 for refractiveindex measurement, the high refractive index and low dispersion material22 was also arranged as a high refractive index material 10 instead ofusing the high refractive index and low dispersion material 21 as shownin FIG. 5B, the quartz glass 6 having a thickness of 1 mm was providedon the high refractive index material 10 with the spacer 11 interposedtherebetween to extend the high refractive index material 10 by pressureapplication. As a result, as shown in FIG. 5E, a sample was formed inwhich an oxygen block layer of the high refractive index material 10having a length of 300 μm from an air interface to the ITO fine-particledispersion material 5 and an oxygen absorption layer of the highrefractive index material 10 on the ITO fine-particle dispersionmaterial 5 were provided. Next, the sample as described above wasirradiated by a high pressure mercury lamp (UL750, manufactured by HoyaCandeo Optronics Corp.) at 20 mW/cm² (illuminance through the quartzglass, illuminance meter: UIT-250, light receiving portion: UVD-S365)for 1,300 seconds (26 J), so that the high refractive index material 10was cured. After the curing was performed, annealing was performed at80° C. for 72 hours. Next, as shown in FIG. 5C, as the post lightirradiation from a quartz glass 6 side, light irradiation was performedusing a high pressure mercury lamp 8 (UL750, manufactured by Hoya CandeoOptronics Corp.) through the quartz glass 6 by adjusting the illuminanceso that the energy at a wavelength of 300 to 400 nm was 100 J (40 mW,2,500 seconds).

The illuminance was determined by measuring light of the high pressuremercury lamp (UL750, manufactured by Hoya Candeo Optronics Corp.) in arange of 250 to 700 nm at 1 nm intervals through the quartz glass 6 by aspectral radiometer (USR-45D-13, manufactured by Ushio Inc.). The datais shown in FIG. 4A.

An accumulated value in a range of 300 to 350 nm was 17.3 mW, anaccumulated value in a range of 350 to 400 nm was 22.7 mW, and the totalwas 40 mW.

Accordingly, the optical element 350 for refractive index measurementwas obtained. In FIG. 5E, the structure of the optical element 350 forrefractive index measurement is shown.

Example 9 <Formation of Optical Element 360 for Refractive IndexMeasurement>

An optical element 360 for refractive index measurement was formed asdescribed below.

Preceding steps before the post light irradiation were the same as thoseof the optical element 350 for refractive index measurement.

After annealing was performed at 80° C. for 72 hours, as the post lightirradiation from a quartz glass 6 side, light irradiation was performedusing a high pressure mercury lamp 8 (UL750, manufactured by Hoya CandeoOptronics Corp.) through a S-TIH11 glass substrate 9 as shown in FIG. 5Dby adjusting the illuminance so that the energy at a wavelength of 300to 400 nm was 50 J (13.2 mW, 3,788 seconds).

The illuminance was determined by measuring light of the high pressuremercury lamp 8 (UL750, manufactured by Hoya Candeo Optronics Corp.) in arange of 250 to 700 nm at 1 nm intervals through the S-TIH11 glasssubstrate 9 by a spectral radiometer (USR-45D-13, manufactured by UshioInc.). The data is shown in FIG. 4B. FIG. 4B shows a spectrum of thehigh pressure mercury lamp for the optical element of the exampleaccording to aspects of the present invention through the S-YIH11substrate.

An accumulated value in a range of 300 to 350 nm was 0.05 mW, anaccumulated value in a range of 350 to 400 nm was 13.15 mW, and thetotal was 13.2 mW.

The ratio of the accumulated value in a range of 300 to 350 nm to thetotal accumulated value in a range of 300 to 400 nm was 0.4%.

Accordingly, the optical element 360 for refractive index measurementwas obtained. In FIG. 5E, the structure of the optical element 360 forrefractive index measurement is shown (the structure is the same as thatof the optical element 330 for refractive index measurement).

Comparative Example 2 <Formation of Optical Element 370 for RefractiveIndex Measurement>

An optical element 370 for refractive index measurement was formed asdescribed below.

First, as shown in FIG. 5A, a spacer 7 having a thickness of 12.5 μm andan ITO fine-particle dispersion material 5 (low refractive index andhigh dispersion material 11) were arranged on a high refractive indexglass (S-TIH11: manufactured by Hoya Corp.) 4 having a thickness of 1mm. In addition, a quartz glass 6 having a thickness of 1 mm was placedon the ITO fine-particle dispersion material 5 with the spacer 7provided therebetween so as to extend the ITO fine-particle dispersionmaterial 5 by pressure application. The structure thus formed wasirradiated by a high pressure mercury lamp (UL750, manufactured by HoyaCandeo Optronics Corp.) at 20 mW/cm² (illuminance through the quartzglass, illuminance meter: UIT-250, light receiving portion: UVD-5365)for 1,300 seconds (26 J), so that the ITO fine-particle dispersionmaterial 5 was cured. After the curing was performed, the quartz glass 6was peeled away, and annealing was performed at 80° C. for 72 hours.Subsequently, after a spacer 11 having a thickness of 50 μm wasarranged, and unlike the case of the optical element 300 for refractiveindex measurement, the high refractive index and low dispersion material22 was also arranged as a high refractive index material 10 instead ofusing the high refractive index and low dispersion material 21 as shownin FIG. 5B, the quartz glass 6 having a thickness of 1 mm was providedon the high refractive index material 10 with the spacer 11 interposedtherebetween to extend the high refractive index material 10 by pressureapplication. As a result, as shown in FIG. 5E, the structure was formedin which an oxygen block layer of the high refractive index material 10having a length of 300 μm from an air interface to the ITO fine-particledispersion material 5 and an oxygen absorption layer of the highrefractive index material 10 on the ITO fine-particle dispersionmaterial 5 were provided. Next, the structure as described above wasirradiated by a high pressure mercury lamp (UL750, manufactured by HoyaCandeo Optronics Corp.) at 20 mW/cm² (illuminance through the quartzglass, illuminance meter: UIT-250, light receiving portion: UVD-S365)for 1,300 seconds (26 J), so that the high refractive index material 10was cured. After the curing was performed, annealing was performed at80° C. for 72 hours.

Accordingly, the optical element 370 for refractive index measurementwas obtained. In FIG. 5E, the structure of the optical element 370 forrefractive index measurement is shown (the structure is the same as thatof the optical element 350 for refractive index measurement).

[Evaluation of Optical Properties (Refractive Indices) of OpticalElements 220, 340, 350, 360, and 370 for Refractive Index Measurement]

By using a refractometer (KPR-30, manufactured by Shimadzu Corp.), therefractive indices of each cured sample were measured as in the case ofExample 1, and from the measured refractive index, the Abbe's number wascalculated.

[Measurement of Oxygen Permeability and Solubility of Material of HighRefractive Index and Low Dispersion Material 22]

As in the case of Example 1, the oxygen permeability and the oxygensolubility were measured using a differential pressure type gaspermeability measurement device (GTR-30XATR, manufactured by GTR TecCorp.) at 23±2° C. (also at 50±2° C. and 80±2° C. for accelerationconversion calculation for subsequent acceleration tests).

<Multilayer Diffractive Optical Element>

Next, after a diffractive optical shape was formed from the lowrefractive index and high dispersion material 11, the high refractiveindex and low dispersion material 21 was laminated thereon withoutforming any space therebetween to form a multilayer diffractive opticalelement, and the evaluation thereof was then performed.

Unlike the cases of Examples 12 and 13, the post radiation was notperformed on the multilayer diffractive optical element.

Example 14 <Formation of Multilayer Diffractive Optical Element 420>

First, as shown in FIG. 6A, an ITO fine-particle dispersion material 5(low refractive index and high dispersion material 11) and a glasssubstrate (hereinafter referred to as “flat glass plate” in some cases)13 having a thickness of 2 mm were arranged in this order on a mold 12having a diffraction grating shape. After curing was performed by lightirradiation using a high pressure mercury lamp (EXECURE250, Hoya CandeOptronics Corp.) at 14.2 mW/cm² for 211 seconds and at 20 mW/cm² for 600seconds (illuminance through the glass substrate 13, illuminance meter:UIT-250, light receiving portion: UVD-5365), as shown in FIG. 6B, theITO fine-particle dispersion material 5 was removed from the mold.Subsequently, annealing was performed in the air at 80° C. for 72 hours,so that a diffraction grating was formed.

The grating height of the diffraction grating measured after theannealing was set to 10.8 μm, the distance from the glass substrate 13to the valley of the grating was set to 2 μm (the average thickness ofthe ITO fine-particle dispersion material 5 was 7.4 μm), and the pitchwas 80 μm.

Next, the ITO fine-particle dispersion material 5 molded on the flatglass plate 13 was set together therewith in a molding jig 15, and onthe ITO fine-particle dispersion material 5, a high refractive indexmaterial 10 (high refractive index and low dispersion material 21) wasdripped (FIG. 7A). Another flat glass plate 13 was provided thereon(FIG. 7B) to extend the high refractive index material 10 by pressureapplication so that a resin thickness was larger than the grating heightby 30 μm and the pitch was 80 μm. As a result, as shown in FIG. 7C, asample was formed in which an oxygen block layer of the high refractiveindex material 10 having a length of 300 μm from an air interface to theITO fine-particle dispersion material 5 and a 35 μm-thick oxygenabsorption layer of the high refractive index material 10 having aheight larger than that of the grating of the ITO fine-particledispersion material 5 were provided. After the sample thus prepared wascured by light irradiation using a high pressure mercury lamp(EXECURE250, Hoya Cande Optronics Corp.) at 14.2 mW/cm² for 211 secondsand at 20 mW/cm² for 600 seconds (illuminance through the flat glassplate 13, illuminance meter: UIT-250, light receiving portion:UVD-S365), annealing was performed at 80° C. for 72 hours.

Accordingly, a multilayer diffractive optical element 420 was formed. InFIG. 7C, the structure of the multilayer diffractive optical element 420is shown (the structure is the same as that of the multilayerdiffractive optical element 400).

Comparative Example 3 <Formation of Multilayer Diffractive OpticalElement 430>

First, as shown in FIG. 6A, an ITO fine-particle dispersion material 5(low refractive index and high dispersion material 11) and a glasssubstrate (hereinafter referred to as “flat glass plate” in some cases)13 having a thickness of 2 mm were arranged in this order on a mold 12having a diffraction grating shape. After curing was performed by lightirradiation using a high pressure mercury lamp (EXECURE250, Hoya CandeOptronics Corp.) at 14.2 mW/cm² for 211 seconds and at 20 mW/cm² for 600seconds (illuminance through the flat glass plate 13, illuminance meter:UIT-250, light receiving portion: UVD-5365), as shown in FIG. 6B, theITO fine-particle dispersion material 5 was removed from the mold.Subsequently, annealing was performed in the air at 80° C. for 72 hours,so that a diffraction grating was formed.

The grating height of the diffraction grating measured after theannealing was set to 10.8 μm, the distance from the glass substrate 13to the valley of the grating was set to 2 μm (the average thickness ofthe ITO fine-particle dispersion material 5 was 7.4 μm), and the pitchwas 80 μm.

Next, the ITO fine-particle dispersion material 5 molded on the flatglass plate 13 was set together therewith in a molding jig 15, andunlike the case of the multilayer diffractive optical element 420, thehigh refractive index and low dispersion material 22 was dripped as thehigh refractive index material 10 on the ITO fine-particle dispersionmaterial 5 instead of using the high refractive index and low dispersionmaterial 21 (FIG. 7A). Another flat glass plate 13 was provided thereonto extend the high refractive index material 10 by pressure applicationso that the thickness of the resin was larger than the height of thegrating by 30 μm, thereby forming a sample (FIG. 7C). After the samplethus prepared was cured by light irradiation using a high pressuremercury lamp (EXECURE250, Hoya Cande Optronics Corp.) at 14.2 mW/cm² for211 seconds and at 20 mW/cm² for 600 seconds (illuminance through theflat glass plate 13, illuminance meter: UIT-250, light receivingportion: UVD-S365), annealing was performed at 80° C. for 72 hours.

Accordingly, a multilayer diffractive optical element 430 was formed. InFIG. 7C, the structure of the multilayer diffractive optical element 430is shown (the structure is the same as that of the multilayerdiffractive optical element 420).

<Evaluation of Diffraction Efficiency of Multilayer Diffractive OpticalElement>

The evaluation was performed in accordance with the evaluation method ofan optical element for refractive index measurement.

<Evaluation of Light Resistance of Multilayer Diffractive OpticalElement>

The evaluation was performed in accordance with the evaluation method ofan optical element for refractive index measurement.

<Change with Time of Multilayer Diffractive Optical Element (Evaluationby Oxygen Acceleration Test)>

The evaluation was performed in accordance with the evaluation method ofan optical element for refractive index measurement.

<Evaluation Results> Initial Evaluation Results

In the multilayer diffractive optical elements 420 and 430 each formedfrom the low refractive index and high dispersion material 11 and thehigh refractive index and low dispersion material 21, the diffractionefficiency in the whole visible region was 99.5% or more.

The low refractive index and high dispersion material 11 of the opticalelement 220 for refractive index measurement had refractive indices(n_(g), n_(f), n_(e), n_(d), n_(C))=(1.600, 1.588, 1.577, 1.569, 1.558)and (ν_(d), θ_(gF))=(19.4, 0.41).

The low refractive index and high dispersion material 11 of the opticalelement 340 for refractive index measurement had refractive indices(n_(g), n_(f), n_(e), n_(d), n_(C))=(1.601, 1.589, 1.578, 1.570, 1.560)and (ν_(d), θ_(gF))=(19.6, 0.41).

The low refractive index and high dispersion material 11 of the opticalelement 350 for refractive index measurement had refractive indices(n_(g), n_(f), n_(e), n_(d), n_(C))=(1.600, 1.588, 1.576, 1.568, 1.557)and (ν_(d), θ_(gF))=(18.8, 0.40).

The low refractive index and high dispersion material 11 of the opticalelement 360 for refractive index measurement had refractive indices(n_(g), n_(f), n_(e), n_(d), n_(C))=(1.600, 1.588, 1.577, 1.569, 1.558)and (ν_(d), θ_(gF))=(19.1, 0.41).

The low refractive index and high dispersion material 11 of the opticalelement 370 for refractive index measurement had refractive indices(n_(g), n_(f), n_(e), n_(d), n_(C))=(1.601, 1.589, 1.578, 1.570, 1.560)and (ν_(d), θ_(gF))=(19.6, 0.41).

The evaluation results of the light resistance are shown in Table 1.

As the results of the light resistance, the case in which the change inthe diffraction efficiency was 0.5% or less or the change in therefractive index was less than 0.002 was ranked as A, and the case inwhich the change in the diffraction efficiency was more than 0.5% or thechange in the refractive index was 0.002 or more was ranked as B.

In the multilayer diffractive optical elements 420 and 430 each formedfrom the low refractive index and high dispersion material 11 and thehigh refractive index and low dispersion material 21, the diffractionefficiency in part of the visible region was changed from the initialvalue to 98.8% or less and was out of an acceptable range of 99.0% ormore.

(Refractive Index and Optical Constant)

The low refractive index and high dispersion material 11 of the opticalelement 220 for refractive index measurement had refractive indices(n_(g), n_(f), n_(e), n_(d), n_(C))=(1.599, 1.586, 1.574, 1.567, 1.556)and (ν_(d), θ_(gF))=(18.6, 0.40), and the change in the refractive indexfrom the initial value was considerable, such as −0.001 to −0.002, andwas out of the acceptable range.

The low refractive index and high dispersion material 11 of the opticalelement 340 for refractive index measurement had refractive indices(n_(g), n_(f), n_(e), n_(d), n_(C))=(1.600, 1.587, 1.576, 1.568, 1.557)and (ν_(d), θ_(gF))=(18.8, 0.41), and the change in the refractive indexfrom the initial value was considerable, such as −0.001 to −0.002, andwas out of the acceptable range.

The low refractive index and high dispersion material 11 of the opticalelement 350 for refractive index measurement had refractive indices(n_(g), n_(f), n_(e), n_(d), n_(C))=(1.600, 1.587, 1.576, 1.568, 1.557)and (ν_(d), θ_(gF))=(18.9, 0.41), and the change in the refractive indexfrom the initial value was hardly observed and was within the acceptablerange.

The low refractive index and high dispersion material 11 of the opticalelement 360 for refractive index measurement had refractive indices(n_(g), n_(f), n_(e), n_(d), n_(C))=(1.600, 1.587, 1.576, 1.568, 1.557)and (ν_(d), θ_(gF))=(18.8, 0.41), and the change in the refractive indexfrom the initial value was −0.000 to −0.001 and was within theacceptable range.

The low refractive index and high dispersion material 11 of the opticalelement 370 for refractive index measurement had refractive indices(n_(g), n_(f), n_(e), n_(d), n_(C))=(1.600, 1.588, 1.576, 1.568, 1.557)and (ν_(d), θ_(gF))=(18.6, 0.41), and the change in the refractive indexfrom the initial value was considerable, such as −0.001 to −0.003, andwas out of the acceptable range.

<Results of Oxidation Acceleration Test>

The results of the oxidation acceleration test are shown in Table 1.

A travel distance of oxidation of 2.5 mm or less (2.5 mm) was ranked asA, a travel distance of more than 2.5 mm to 10 mm was ranked as B, and atravel distance of more than 10 mm was ranked as C.

(Travel Speed of Oxidation, Refractive Index, and Optical Constant)

In the optical element 220 for refractive index measurement, the traveldistance of oxidation from the end portion was 15.3 mm which was largerthan the width of 2.5 mm of the annular zone and was extended in theeffective diameter zone by 12.8 mm.

An oxidized portion of the low refractive index and high dispersionmaterial 11 had refractive indices (n_(g), n_(f), n_(e), n_(d),n_(C))=(1.601, 1.589, 1.578, 1.572, 1.561) and (ν_(d), θ_(gF))=(20.3,0.42), and the change in the refractive index from the initial value was+0.001 to +0.002 and was out of the acceptable range.

In the optical element 340 for refractive index measurement, the traveldistance of oxidation from the end portion was 2.3 mm which was withinthe width of 2.5 mm of the annular zone. Since the end portion wassmall, the refractive index could not be measured.

In the optical element 350 for refractive index measurement, the traveldistance of oxidation from the end portion was 15.3 mm which was largerthan the width of 2.5 mm of the annular zone and was extended in theeffective diameter zone by 12.8 mm.

An oxidized low refractive index and high dispersion material 11 hadrefractive indices (n_(g), n_(f), n_(e), n_(d), n_(C))=(1.602, 1.590,1.580, 1.573, 1.562) and (ν_(d), θ_(gF))=(20.5, 0.42), and the change inthe refractive index from the initial value was +0.002 to +0.005 and wasout of the acceptable range.

In the optical element 360 for refractive index measurement, the traveldistance of oxidation from the end portion was 15.3 mm which was largerthan the width of 2.5 mm of the annular zone and was extended in theeffective diameter zone by 12.8 mm.

An oxidized low refractive index and high dispersion material 11 hadrefractive indices (n_(g), n_(f), n_(e), n_(d), n_(C))=(1.602, 1.590,1.580, 1.573, 1.562) and (ν_(d), θ_(gF))=(20.5, 0.42), and the change inthe refractive index from the initial value was +0.002 to +0.004 and wasout of the acceptable range.

In the optical element 370 for refractive index measurement, the traveldistance of oxidation from the end portion was 15.3 mm which was largerthan the width of 2.5 mm of the annular zone and was extended in theeffective diameter zone by 12.8 mm.

An oxidized low refractive index and high dispersion material 11 hadrefractive indices (n_(g), n_(f), n_(g), n_(d), n_(C))=(1.602, 1.590,1.580, 1.573, 1.562) and (ν_(d), θ_(gF))=(20.5, 0.42), and the change inthe refractive index from the initial value was +0.001 to +0.003 and wasout of the acceptable range.

In the multilayer diffractive optical element 420, the travel distanceof oxidation from the end portion was 2.3 mm which was within the widthof 2.5 mm of the annular zone. The change in the diffraction efficiencyand inconveniences of the whole element were not observed.

In the multilayer diffractive optical element 430, the travel distanceof oxidation from the end portion was 15.3 mm which was larger than thewidth of 2.5 mm of the annular zone and was extended in the effectivediameter zone by 12.8 mm.

When the diffraction efficiency of an oxidized element portion wasmeasured, the diffraction efficiency in part of the visible region waschanged from the initial value to 98.8% or less and was out of anelement acceptable range of 99.0% or more.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

What is claimed is:
 1. A method for manufacturing an optical elementcomprising: providing a first layer comprising a first material on atransparent substrate, the first material containing a monomer oroligomer of a first energy curable resin composition; curing the firstlayer by light to provide a cured first material; providing a secondlayer comprising a second material containing a monomer or oligomer of asecond energy curable resin composition on the cured first material;curing the second layer by light irradiation; performing a heattreatment on the cured first material and the cured second material; andperforming post light irradiation on the cured first material processedby the heat treatment.
 2. The method for manufacturing an opticalelement according to claim 1, wherein the first material contains fineparticles of a transparent conductive material.
 3. The method formanufacturing an optical element according to claim 2, wherein the fineparticles of the transparent conductive material are fine particlescomprising at least any one of zinc oxide (ZnO), indium oxide, tinoxide, antimony oxide, indium tin oxide (ITO), antimony-doped tin oxide(ATO), zinc-doped indium oxide (IZO), aluminum-doped zinc oxide (AZO),and fluorine-doped tin oxide (FTO).
 4. The method for manufacturing anoptical element according to claim 3, wherein the fine particles of thetransparent conductive material are fine particles of indium tin oxide(ITO).
 5. The method for manufacturing an optical element according toclaim 1, wherein the second material contains fine particles of zirconiaor alumina, and the monomer or oligomer of the second energy curableresin composition.
 6. The method for manufacturing an optical elementaccording to claim 1, wherein the curing the second layer includesproviding a second transparent substrate on the second layer, andperforming light irradiation from above the second transparentsubstrate.
 7. The method for manufacturing an optical element accordingto claim 1, wherein the performing the heat treatment includes heatingthe cured first material and the cured second material at 60° C. or moreand 120° C. or less for 24 hours or more and 120 hours or less.
 8. Themethod for manufacturing an optical element according to claim 1,wherein the performing the post light irradiation includes irradiatingwith light having a wavelength of 300 nm or more and 400 nm or less, andan amount of irradiation of the light having a wavelength of 300 nm ormore and 400 nm or less is 12 J/cm² or more and 150 J/cm² or less. 9.The method for manufacturing an optical element according to claim 8,wherein a ratio of light having a wavelength of 300 nm or more and 350nm or less to a total of the light having a wavelength of 300 nm or moreand 400 nm or less is 0% or more and 10% or less.